Biology Unit 1-5 (no 4) Flashcards
1
Q
What is a species?
A
A species is a group of organisms that share common physical characteristicsMembers of the same species are capable of breeding together to produce viable offspring
2
Q
What is evolution?
A
Evolution is the cumulative change in the heritable characteristics of a population
3
Q
What happens in speciation?
A
Evolution can lead one species to diverge into two separate species. One species can gradually diverge into separate species by evolution
4
Q
What do fossils tell us about evolution?
A
- Fossils demonstrate gradual change in physical characteristics of a species - Fossils demonstrate species extinctionFossils record the gradual change in the characteristics of a species over long periods of time
5
Q
What is a homologous structure?
A
A homologous structure is a physical characteristic shared by related species
6
Q
What does the pentadactyl limb tell us about mammals?
A
All mammals are descended from a common ancestor The genetic code is universal. This provides evidence that all living species share common ancestors.
7
Q
Outline the difference between artificial and natural selection.
A
Artificial selection:Organisms are selected for a purpose (better tasting food crops, smarter sheepdogs, faster racehorses)Artificial selection is carried out by humansNatural selection:Organisms are not selected for a purpose… instead the focus is on survivalNatural selection is driven by environment
8
Q
How does artificial selection demonstrate evolution?
A
Selective breeding of domesticated animals (pets) shows this because they have evolved through human selection
9
Q
What is a cline?
A
A cline is a gradation in one or more characteristics within a species.
10
Q
Outline five types of evidence which support thetheory of evolution by natural selection
A
? fossils/paleontological: fossilized horse ancestors/other evidence? homologous structures: pentadactyl limb/vertebrate embryos/other? Selective breeding of domesticated animals shows that artificial selection can cause evolution? recent observed evolution: resistance to antibiotics/melanistic (dark color) insects in polluted areas/other recent example? geographic distribution: ring species/other evidence from geographical distribution? biochemistry: cytochrome c/other biochemical evidence
11
Q
What explains similarities in structure when there are different function?
A
Evolution of homologous structures by adaptive radiation explains the similarity even when they have different functions.
12
Q
What is adaptive radiation?
A
When organisms come from the same origin, like from an ancestor that had a pentadactyl limb, and they become different because they perform different functions.
13
Q
What is a convergent evolution?
A
Organisms that have had different origins and have become similar because they perform the same or a similar function.
14
Q
Give evidence from patterns of variation.
A
Example: human skin colour as evidence for evolution: • People with darker skin colour have evolved in places with high UV light –> protect them from cancer • People with lighter skin colour have evolved in places with low UV light –> helps them to generate enough Vitamin D
15
Q
What is gradual divergence?
A
Continuous variation across the geographical range of related population matches the concept of gradual divergence.
16
Q
Does the continuous range in variation match the belief that species were created as distinct types of organisms?
A
No it does not. Continuous range in variation is not constant or unchanging. It provides evidence for evolution and origin of species by evolution.
17
Q
How did melanistic insects evolve?
A
Dark varieties of typically light coloured insects are called melanistic. The most famous example is the peppered moth which developed the melanistic variety in polluted industrial areas for better camouflage (change in natural environment)
18
Q
Why do living organisms face a struggle for survival?
A
- All species have great potential fertility2. Population sizes show long term stability3. Environmental resources are limitedLiving organisms have to compete with other members of their species in order to survive
19
Q
Why do living organisms face a struggle for survival?
A
- All species have great potential fertility2. Population sizes show long term stability3. Environmental resources are limitedLiving organisms have to compete with other members of their species in order to survive
20
Q
What do members of a species show?
A
Living organisms show an enormous range of variation. No two living organisms are ever truly identical, even if they are genetic clones
21
Q
Only under what condition can natural selection occur?
A
Natural selection can only occur if there is variation among members of the same species.Adaptations are characteristics that make an individual more suited to survive in its environment and successfully reproduce.
22
Q
What promotes genetic variation?
A
Independent assortment, Meiosis, Gene Mutation and sexual reproduction
23
Q
How does natural selection lead to evolution?
A
- Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring2. individuals that reproduce pass on characteristics to their offspring3. natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the species
24
Q
Explain how the use of antibiotics has led to the evolution of resistant bacteria
A
- members of a population of the same species show variation- some organisms are more likely to survive due to selective advantage- these variations may be genetically controlled/heritable- these genes are most liekly to be passed on to offspring - this can change the characteristic of the population- bacteria can noramlly be killed by antibiotics- anti biotics impose a selection pressure - if few bacteria have natural resistance to the antibioticthey will survive- if the resistance is heritable they will pass it on their offspring- they will reproduce/evolve to form bacterial colonies resistant to antibiotics.
25
Explain how the use of antibiotics has led to the evolution of resistant bacteria
- members of a population of the same species show variation- some organisms are more likely to survive due to selective advantage- these variations may be genetically controlled/heritable- these genes are most liekly to be passed on to offspring - this can change the characteristic of the population- bacteria can noramlly be killed by antibiotics- anti biotics impose a selection pressure - if few bacteria have natural resistance to the antibioticthey will survive- if the resistance is heritable they will pass it on their offspring- they will reproduce/evolve to form bacterial colonies resistant to antibiotics.
26
Briefly explain Darwin`s theory of evolution.
• Species tend to produce more offspring than the environment can support• the consequence of the potential overproduction of offspring is a struggle for survival• Mutation, meiosis and sexual reproduction cause variation (different characteristics) between individuals in a species.• Adaptations are characteristics that make an individual suited to its environment.• Individuals that are better adapted tend to survive and produce more offspring while the less well adapted tend to die or produce fewer offspring.• Individuals that reproduce will pass on characteristics to their offspring.• This selective "pass on characteristics" is called natural selection.• Natural selection leads to change in allele frequency.• Characteristics acquired during the lifetime of an individual (Eg. Learned skills) are not heritable. Therefore, it does not affect evolution.
27
What is an acquired characteristic?
An Acquired characteristic is a change that happens to an organism during its lifetime. These types of characteristics do not affect DNA and are not heritable.
28
Discuss evidence against the theory of evolution by inheritance of acquired characteristics.
? This is an incorrect theory stating that characteristics acquired during the lifetime of an individual can be passed on to next generation.? Acquired characteristics example: giraffes reach for leaves on tall tree, therefore their neck becomes longer, over many generations, giraffes have long neck.? This theory is incorrect because it relies on phenotypic inheritance, not genotypic inheritance /somatic changes cannot be passed on? example: if tail cut off rat -- offspring still have tails? cannot be repeated experimentally since very many generations would be necessary? also mutations would have to be eliminated in such anexperiment -- impossible
29
Explain with an example of natural selection causes progressive change.
Darwin collected finches which varied in sizes and shapes of their beaks.Beaks characters and diet are closely related, when one changes the other does also. Medium ground finch can eat large and small seeds whereas small finch can only eat small seeds.Daphne Major absence of small ground finch so... When eating small seeds the medium ground finch was smaller in body and beak size. When there was a shortage, the larger beaked individuals survived.Variation in beak and body size is mostly due to genes but the environment has some effect. The proprtion of the variation due to genes is called heritability.
30
What is progressive change?
Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics.
31
What is adaption?
Adaption are characteristics that make an individual suited to its environment.
32
What are organisms classified into?
All organisms are classified into three domains. (Archaea, eubacteria and eukaryote should be used for the three domains. Members of these domains should be referred to as archaeans, bacteria and eukaryotes)
33
Why are viruses not classified as living organisms?
* They are acellular: viruses are not composed of cells
* They have no metabolism: metabolism is the sum total of all biochemical reactions that occur inside cells… without cells viruses have no metabolism
* They are unable to reproduce independently viruses must inject their genetic material into a host cell in order to replicate themselves
34
How do taxonomist classify species?
They use the hierarchy of taxa.
35
What are the principal taxa for classifying eukaryotes?
Kingdom, Phylum, Class, Order, Family, Genus, SpeciesKing Phillip Came Over For Good Spaghetti
36
Classify one animal species from domain to species level.
LionKingdom: AnimaliaPhylum: ChordataClass: MammaliaOrder: CarnivoraFamily: FelidaeGenus: PantheraSpecies: leo
37
Classify one plant species from domain to species level.
Dog RoseKingdom: PlantaePhylum: AngiospermsClass: EudicotOrder: RosalesFamily: RosaceaeGenus: RosaSpecies: canina
38
Why do we use the system of binomial nomenclature for naming?
- Universal system helps international collaboration - Names are descriptive (is Latin)- The bionomial system allows us to identify species that are closely related (i.e. Rattus norvegicus and Rattus rattus)
39
Which plant phyla has vascular tissues?
Filicinophyta
40
What are four plant phyla? (give example)
Bryophyta - mossesFilicinophyta - ferns Coniferophyta - conifers Angiospermophyta - flowering plants
41
What characteristics identify Bryophyta?
* have no roots
* have simples leaves/stems
* produce spores in capsule
* are nonvascular - exhibit alternation of generations/ is a significant gametophyte generation
42
What characteristics identify Filicinophyta?
* have roots, stems and leaves
* (often) have divided/pinnate leaves
* produce spores in sporangia/ spores on undersides of the leaves
* exhibit alternation of generations - have primitive vascular tissues
43
What characteristics identify Coniferophyta?
* have woody stems
* (often) have narrow leaves/needles/scales
* produce seeds in cones/ unenclosed seeds
44
What characteristics identify Angiospermophyta?
- have flowers - have ovules in ovaries - produce seeds (with hard coats) in fruits
45
What are the different phyla for animals?
Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, Arthropoda
46
What characteristics identify Porifera?
• No clear symmetry• Attach to a surface under water • Pores (holes) extend through the body• No mouth or anus
47
What characteristics identify Cnidaria
• Radial symmetry• Tentacles sometimes with stinging cells• Mouth but no anus (pocket gut)
48
What characteristics identify Platyhelminthes?
• Bilateral symmetry• Flat body• No segmentation• mouth but no anus (pocket gut)
49
What characteristics identify Annelida?
• Bilateral symmetry• Often have bristles• Clear segmentation• Mouth and anus present (tube gut)
50
What characteristics identify Mollusca?
• Muscular foot or mantle• Usually have a shell (not squid or octopus)• No visible segmentation• Mouth and anus are present (tube gut)
51
What characteristics identify arthropoda?
• Bilateral symmetry• Hard exoskeleton• Clear segmentation and jointed appendages (arms, legs, feelers, claws)
52
What are the classes of the phylum of chordata?
Birds, Mammels, Amiphibians, Reptiles, Fish
53
What are external recognition of birds?
* A bird is an animal with feathers.
* Birds have two legs and two wings.
* Birds have a beak or a bill.
* They lay eggs on land
* They are warm-blooded
54
What are physical characteristics of mammels?
* They have fur or hair.
* The babies drink milk from their mother's bodies.
* They have four limbs (arms, legs, flippers).
* They are warm-blooded.
* Most mammals are born alive.
* They breathe air through lungs.
55
What are physical characteristics of amphibians?
* Cold blooded
* Live both under water and on land (live in damp places)
* Lay jelly covered eggs in water
* Breath with gills (babies)
* Moist skin
56
What are physical characteristics of reptiles?
* They have dry, scaly skin.
* They have short legs or no legs at all.
* They breathe with lungs.
* They are cold-blooded.
* Most young reptiles hatch from eggs on land
57
What are physical characteristics of fish?
* Fish are cold blooded.
* Fish lay eggs.
* Most fish are covered with scales
* They have fins not legs.
* Fish live in water and breathe through gills.
58
Distinguish between the 3 domains of classification
Bacteria (exp: E.Coli)
* Prokaryote = no nucleus Cells walls contain peptidoglycan NO Histone proteins NO introns
Archae (Exp: Halobacteria)
* Prokaryote = no nucleus Cells walls do not contain peptidoglycan Histone proteins bound to DNA Some genes contain introns
Eukaryotes (Exp: Saccharomyces)
* DNA inside a nuclear envelope = Eukaryote Histone proteins Genes contain introns frequently Cell walls not made of peptidolgycan
59
What does a natural classification include?
In a natural classification, each taxon includes all of the organisms that descended from one common ancestor
60
What does an artificial classification include?
In a artificial classification, the taxa do not include of descended from one common ancestor.
61
Outline two advantages of natural classification
* It allows us to make predictions about living species, based on what we know about other closely related organisms
* It helps us to find characteristics to identify a species
62
What happens when taxonismist find new evidence?
Taxonomists sometimes reclassify groups of species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species
63
What is a clade?
A group of organism that includes all of the evolutionary descendants of a common ancestor
64
What is a cladogram?
A tree diagram that shows the most probable sequence of divergences in a clade
65
According to this diagram are reptiles a clade?
No reptiles are not a clade because they do not include all descendant of a common ancestor.
66
How do you identify members of a clade?
Evidence for which species are part of a clade can be obtained form the base sequence of a gene or the corresponding amini acid sequence.
67
What is a molecular clock?
Sequence differences accumulate gradually so there is a positive correlation between the number of differences between two species. Changes in the DNA base sequence for a specific gene expected to occur gradually, at a constant rate
68
What is an analogous trait?
An analogous trait is a characteristic that two organisms share due to convergent evolution, not common ancestry
69
What is a homologous trait?
A homologous trait is a characteristic that two organisms share due to common ancestry
70
How are cladograms and reclassification related?
Evidence from claditics has shown that classifications of some groups based on structure did not corespond with the evolutionairy origins of a group of species
71
What is falsification?
Falsification of theories with one theory being susperseded by another plant families have been reclassified as a result of evidence from cladistics.
72
What is an example of a plant taxon that has been reclassified in light of new evidence?
Figwort family is an example of a plant taxon that has been reclassified in light of new evidence from DNA analysis and cladistics
73
Give an exceptions of the cell theory.
Giant algae (mermaid's wineglass) The entire organism is made from only 1 cell that can reach to 7cm. The orgasm is not divided into smaller cells. Aseptate fungusMany fungi are aseptate, this means that the cell walls that divide the cells have broken down. The cytoplasm is continuous with many nuclei. Skeletal musclesCells fuse together to form muscles fibers. It is impossible to tell where one cell ends and next begins. Slime mold They reproduce when many cells fuse together to form a multi nucleate jelly.
74
How can you calculate magnification?
(image size)/(actual size)=magnification
75
What are the three statements of the cell theory?
1. All living organisms are made of cells2. A single cell is the smallest unit of life3. Cells come from the division of pre-existing cells.
76
What is the thickness of plasma membranes?
7-8 micrometers
77
What is the size of a liver cell?
30 micrometers
78
What is the size of a plant cell?
50 micrometers
79
What is the size a amoeba?
1000 micrometers
80
What is the size a amoeba?
1000 micrometers
81
How many mm in 200 micrometers?
0.2 mm
82
How many micrometers in 10 mm?
10,000 micrometers
83
How many nm in 2 mm?
2,000 micrometers = 2,000,000 nm
84
How many micrometers in 0.8 mm?
800 micrometers
85
How many mm in 5 micrometers?
0.005 mm
86
How many micrometers in 23.4mm?
23,400 micrometers
87
How many micrometers in 23.4mm?
23,400 micrometers
88
What are the 7 factors that qualify something to be alive?
Nutrition, metabolism, growth, response, excretion, homeostasis, reproduction.
89
Briefly explain metabolism.
All organisms are sustained by chemical reactions that take place inside their cells, including respiration to release energy.
90
Briefly explain homeostasis
Keeping conditions inside the organism within tolerable limits. (Release Sweat and shiver)
91
As the volume of a cell increases, what happens to heat production?
Heat production increases.
92
As the volume of a cell increases, what happens to the production of waste products?
The production of waste products increase.
93
As the volume of a cell increases, what happens to the usage of nutrients and oxygen?
The usage of nutrients and oxygen increases as it demands more.
94
As the volume of a cell increases, what happens to the surface area to volume ratio?
The surface area to volume ratio decreases as volume increases.
95
Why can a cell not grow to the size of a football field?
1. As the volume increases, heat production significantly increases while surface area is not enough to balance heat loss, causing the cell to overheat. 2. As volume increases waste production increases while the surface area to volume ratio decreases, waste excretion is harder. 3. As volume increases, resource consumption directly increases, while resource absorption does not increase as much, causing a limitation towards absorption.
96
Suggest three features of a cell that could increase surface area.
1. In the small intestine, microvilli increase surface area.2. Plant roots increase surface area for absorption of nutrients. 3. Red blood cells have a donut shape which increase surface area.
97
What is an emergent property?
Emergent properties arise from the interation of compnent parts: the whole is greater than the sum of of its parts
98
What is specilization in cells?
Different cells are dedicated to carrying out different functions. Specilized cells have their own structures to enable them to perform their roles
99
What do motor neurons do?
Is responsible for carrying out electrical signals over long distance
100
What do red blood cells do?
Thye are responsible for the transportation of oxygen.
101
What is a stem cell?
Stem cells are the primary cells that are undifferentiatedHave the capacity to differentiate themselves
102
What does it mean when cells differentiate?
When cell differentiate, they become specialized cells.To become speialized cells, they turn off unnecessary genes
103
What is necessary for embryonic development?
The capacity of stem cells to divide and differenciate along different pathways.This makes them suitable for treatments.
104
What diseases can be treated with embryonic stem cells?
Heart failureheart muscles are usually damaged so adult stem cells can be used to replce in order to repair damamged heart muscles. Umbiblical Stem cellFaconi anaemia is a blood disease that can be treated using umbiblical stem cells.
105
What is a prokaryote?
A prokaryote is a cell without a nucleus. All bacteria are prokaryotic.
106
What does a prokaryotic cell look like? Label 8 cell components.
Cell wallPlasma MembraneFlagellum PiliCytoplasm RibosomesNucleoid DNA
107
What is the function of a cell wall?
Provides support and keeps the cell in the right shape and protects the cell from outside damage.
108
What is the function of Pilus?
Enables the cell to stick other surfaces, or other bacterial cells.
109
What is the function of a flagellum?
It is a "propeller" that enables the cell to move.
110
What is the function of plasma membrane?
The plasma membrane regulates the movement of materials in and out of the cell.
111
What is the function of cytoplasm?
Most made out of water. the place where most chemical reactions take place.
112
What is the function for ribosomes?
Produces protein. Free ribosomes in prokaryotes are size 70S while eukaryotes are 80S
113
What is a nucleoid?
A nucleoid only applies for prokaryotes. It's a region where the naked DNA is located
114
How do prokaryotes multiply?
Prokaryotes multiply through binary fission.
115
How does binary fission work?
The DNA duplicates itself in the cellThen the cell elongatesFinally, the cell will split into two new cells.
116
Name at least 8 organelles and their function of an animal cell.
RibosomesNucleusGolgi apparatus MitochondriaCytoplasmRough endoplasmic reticulumPlasma membrane Vesicles LysosomesVacuole
117
Name at least 8 organelles and their functions of a plant cell.
RibosomesCell wallNucleusGolgi apparatus MitochondriaCytoplasmRough endoplasmic reticulumPlasma membrane Vesicles LysosomesVacuole
118
What are two distinct differences between Prokaryotes and Eukaryotes?
Eukaryotes are compartmentalized while prokaryotes are not. Prokaryotes do not have a nucleus while eukaryotes have a nucleus protecting their DNA
119
What is the function of a mitochondria?
It's the site for aerobic respiration. This means that converts and so produces energy.
120
What is the function of a golgi apparatus?
They involve the the processing and packaging of protein molecules which are using the vesicles send outside the cell.
121
What is the function of Rough Endoplasmic Reticulum?
The RER produces protein that is then sent to the golgi apparatus.
122
What is the function of a Vesicle?
small membrane bound sack containing biological molecules that can transport from the cell
123
What is the function of lysosomes?
Small membrane bound sack containing digestive enzymes.
124
What is the function of Vacuole?
Vacuoles are large membrane bound sacks used for storage ie. waste, sugar, salt, water
125
What do lots of Mitochondria indicate?
Many mitochondria indicate that the cell is in high demand for energy. It is a very active cell.
126
What do lots of chloroplasts indicate?
The cell is doing lots of photosynthesis.
127
What do lots of RER indicate?
Lots of RER indicates the cell is producing lots of protein to be exported.
128
Compare Eukaryotes and Prokaryotes.
Eukaryotes have a nucleus which protects the DNA mixed with protein. Prokaryotes do not have a nucleus. Their naked DNA is located in the nucleoid.
Eukaryotes are compartmentalized. Prokaryotes are not compartmentalized.
Eukaryotes have mitochondria. Prokaryotes do not have mitochondria.
Eurkaryotic ribosomes are 80S. Prokaryotic ribosomes are 70S
Eukaryotes do not have a flagellum. Prokaryotes have a flagellum.
Eukaryotes do not have pili. Prokaryotes have pili.
List similarities as well
129
Compare Plant and Animal cell
Plant cells have chloroplasts. Animal cells do not have chloroplasts.
Plant cells have cell walls. Animal cells can change shape as they do not have cell walls.
Plant cells have large, central vacuoles. Animal cells only sometimes have vacuoles. If they do, they are smaller and temporary.
List similarities.
130
Why are electromicroscopes better than microscopes?
They have higher resolution due to technology.
131
Outline the structure of a phospholipid layer.
Hydrophilic heads (phosphate group, glycol) and Hydrophobic tails (2 fatty acids)
132
What does amphipathic mean?
Amphipathic means that the organism is partly hydrophilic as well hydrophobic, like a phospholipid.
133
How is the phospholipid bilayer maintained?
The hydrophilic heads are pointed outwards. They are attracted to the water inside and outside of the cell. The hydrophobic tails are pointed inwards as they avoid contact with the water. They are also attracted to each other. The nature of amphipathic nature of phospholipids helps to ensure stability of the plasma membrane.
134
How did the evidence from electron microscopy support the Davson and Danielli model?
In their model, the phospholipid layer is sandwiched by two layers of protein as they know that they contain protein due to the evidence of membranes being isolated from red blood cells contain protein. This as well as the fact that the surface of an actual biological membrane is more wettable than an artificial, lead them to think that membranes are coated by protein which absorb the water.
135
How was the Davson and Danielli model proven wrong by Singer Nicholson?
A membrane with an outside layer of protein would not be stable as it block the absorbance of water for the hydrophilic part of the phospholipid. Membrane proteins can change their positions within the lipid layer.So, the new model showed that Proteins are individually embedded in the lipid layer. This lets the hydrophilic portions expose to its maximum to water which keeps the layer stable.
136
Draw a full 2D diagram of a phospholipid layer. Label it.
* Phospholipid bilayer (hydrophilic head & hydrophobic tails)
* Cholesterol
* Glycoprotein
* Integral proteins
* Peripheral proteins.
137
What is the function of cholesterol?
Cholesterols are part of animal membranes. They make the layer less fluid.
138
What is a protein called that goes all the way through the bilayer?
An integral protein.
139
What is a protein called that does not reach all the way through the bilayer?
a peripheral protein
140
What is Diffusion?
Diffusion is a passive movement of particles from a region of high concentration to low concentration.
141
What types of membrane transport are there?
There are two types of diffusion. simplified and facilitated. There is also active transport and osmosis. There is also exocytosis and endocytosis.
142
What is the difference between diffusion and active transport?
Diffusion does not require energy. Active Transport goes against the concentration gradient while Diffusion goes down the concentration gradient.
143
Compare simplified and facilitated diffusion.
Both do not require energySimplified diffusion does not require protein channels. Facilitated diffusion required protein channels. In both diffusions, substances move down a concentration gradient.
144
What is active transportation?
This is the movement of substances against the concentration gradient. This means it goes from a region of low concentration to high concentration. Unlike passive transportations, this requires energy. Protein pumps are also needed for active transportation. .
145
What is osmosis?
Osmosis is the movement of water through a semipermeable membrane, from a region of high water concentration to a region of low water concentrationOsmosis does not require energy. It is an example of passive transportation.
146
How are tissues or organs used in medical procedures?
In order to use tissues or organs in medical procedure, the organs must be bathed in a solution of the same osmolarity as the cytoplasm of the cell in order to prevent osmosis.
147
When doing an experiment with potato chips in different concentrations of salt we found that the sizes of them change. Work out the osmolarity of the potato's cytoplasm.
The point where the line crosses the X axis, gives us an estimate of the concentration of the cytoplasm of the potato cells. We can also see that at 0.16mol/dm3 the size of the potato chip should not change.
148
Why is the membrane so efficient for exo- or endocytosis?
Due to the fluidity of the plasma membrane, the membrane can change its shape, break and re-form during endocytosis or exocytosis. Both membrane transportations require energy.
149
How does endocytosis work?
Endocytosis works through the change of shape of the membrane. The membrane will sink inwardly, forming a pit which encloses the material coming into the cell. The the membrane seals back on itself as the edges fuse. This vesicle then will break away from the membrane and move into the cytoplasm. The particles have now entered the cell enclosed by a vesicle.
150
How are vesicles used to transport material?
In both exocytosis and endocytosis, vesicles are used to transport materials that are too large to enter the cell through passive or active transport. In exocytosis, protein produced in the RER is send to the golgi apparatus via vesicles which are then packaged and processed to be send via vesicles to the plasma membrane. The vesicle attaches itself to the membrane and fusion to the membrane releases the material inside the vesicle.
151
How did Pasteur disprove the spontaneous cell theory?
The spontaneous cell theory, proposed that cells just spontaneously appear. Yet, Pasteur's experiment proved that bacteria could only come from other bacteria. This means that cells can only come from preexisting cells.
152
Where did the first cell come from?
The first cell is an exception to Pasteur's theory as the first cell is an emergent property of non living chemicals.
153
If the first cell was created through non-living chemicals, can this still happen today?
No, this can no longer happen today because our environment has become to sterile. This means that even if the chemicals existed, they would probably be eaten by some of our bacteria today.
154
How did mitochondria and chloroplasts become part of a eukaryotic cell?
The theory holds that mitochondria and chloroplasts started out as living bacteria inside of a eukaryote. As the relationship benefited both, it became permanent.
155
Why is it theorized that mitochondria and chloroplasts started out as bacteria inside of a eukaryote?
Mitochondria has its own DNA. Mitochondria has 70S ribosomes like prokaryotes. They are about the same size as prokaryotes.They reproduce through a similar process of binary fission.
156
Why do eukaryotes need to do mitosis?
1. embryonic development2. repair3. growth4. asexual reproduction
157
Draw and explain the process for mitosis.
Mitosis Prophase The nuclear is broken down. The DNA condenses to be visible chromosomes through supercoiling. Spindle fibers grow from each of centriolesMetaphase The chromosomes line up at the equator. The spindle fibers attach themselves to each chromatid.Anaphase The spindle fibers shorten as the chromatids are now pulled apart into sister chromatids.Telophase Chromosomes uncoil. The 2 nuclear membranes form around each pole. Spindle fibers break down.Interface
158
What happens in the interface?
Interphase is a very active part of the cell cycle. In this part, many processes occur in the nuclear and cytoplasm.
159
In what phase of the cell cycle is this cell in?
Interphase
160
In what phase of the cell cycle is this cell in?
Prophase
161
In what phase of the cell cycle is this cell in?
Metaphase
162
In what phase of the cell cycle is this cell in?
Anaphase
163
In what phase of the cell cycle is this cell in?
Telophase
164
In what phase of the cell cycle is this cell in?
Cytokinesis
165
How do you calculate a mitotic index?
Mitotic index = (total number of cells doing mitosis)/(total number of cells)
166
What is the mitotic index used for?
Mitotic index is often used for doctors to determine whether the patient has cancer, as well as the chance of the patient's survival, and whether or not the patient will respond positively or negatively to chemotherapy.
167
Compare cytokinesis between animal and plant cell.
Animal cells do not have cell walls. Plant cells have cell walls that is created through a cell plate. Vesicles do not line up in an Animal Cell.Vesicles line up along the equator in Plant cells. Animal cells are separated by cleavage furrow. Plant cells are not separated by cleavage furrow. List similaritieseg. Both plant and animal cells' cytoplasm is separated.Both plant and animal cells form 2 genetically identical daughter nuclei.
168
What are cyclins?
Cyclins are proteins that control the progression of cells through the cell cycle by activating enzymes.
169
What causes cancer?
Mutagens: physical or chemical factor that causes DNA mutations physical (UV, Xray, gamma radiation) Chemical (polonium, carbon monoxide, radium)
Oncogenes: genes that have the potential to cause cancer. Usually have rapid growthMetastasis: when cancerous cells break off from a tumour, they travel in the body stream, and cause new tumours elsewhere.
170
What kind of cell division does tumour present?
Tumour presents an example of an uncontrolled cell division.
171
Draw and label a diagram of a water molecule
Water is made out of the covalent bondings of two positive hydrogen atoms and one negative oxygen atom.
172
What is a hydrogen bond?
It is the bond between different water molecules. This is due to the fact that the water molecule has polar charged regions that attract itself to other water molecules' polar regions.
173
What is a thermal property of water?
Thermal properties of water include heat capacity, boiling and freezing point.
174
Does water have a low or high heat capacity?
Water has a high heat capacity meaning that it takes much more energy to increase change its temperature than, say methane.
175
Why does water have a high heat capacity?
Water has a high heat capacity due to its strong hydrogen bonds that make it difficult for them to break without sufficient energy. This means that water remains relatively stable. This property is often used for animals as they can cool themselves or warm themselves in the water.
176
Water takes boils at a higher temperature than methane. Why is this?
Due to water's high latent heat capacity, it takes water molecules much more energy to convert from liquid to gas. This means that because of the strong hydrogen bonds, they require a lot of energy to break apart in order for water to evaporate.
177
Why is sweating ineffective in a very humid climate?
Sweat is released in order cool the body down, as the sweat evaporate, leaving the surface of the skin cooler as all the high energy (hot) molecules are released into the atmosphere. In a humid climate, the air already contains lots of water which means that there is not enough space for the sweat to evaporate, leaving the body hot and drenched.
178
Why is the high boiling point of water vital to life?
The high boiling point enables organisms to survive in hotter climates. If water did not have such high specific heat capacity, organisms would boil along the water and be unable to survive.
179
How does water in its solid state become beneficial to organisms?
When water freezes, it becomes less dense. This means that the ice blocks will float atop of the water. Ice covered surface on lakes and seas acts as an insulator for the water underneath to maintain habitats for organisms.
180
How do plants benefit from water properties?
One of the properties water has is its cohesion. Due to the hydrogen bonds, water is able to be transported from the roots to leaves through long columns.
181
What property is present when sugar is mixed with water?
When sugar is mixed into water, it dissolves presenting water's solvent properties because of its polarity.
182
How is oxygen transported in blood?
Oxygen has low solubility in water and therefore needs to be transported through haemoglobins.
183
Which molecules have high solubility in water and can be transported through blood plasma?
Glucose, amino acids and sodium chloride are soluble.
184
If molecules have low solubility in water, how can they be transported in blood?
Molecules like fats and cholesterol have low solubility, and need to be transported inside lipoproteins in blood.
185
Which elements make up carbohydrates?
CHO - Carbon, Hydrogen, Oxygen
186
Which elements make up Proteins?
CHON - Amino acid: Carbon, Hydrogen, Oxygen and Nitrogen
187
What elements make up Lipids?
CHO - Carbon, Hydrogen, Oxygen
188
What elements make up DNA?
CHOP - Carbon, Hydrogen, Oxygen, Phosphate
189
What is the definition of inorganic chemicals?
Mineral compounds such as salts, i.e. sodium chloride, potassium sulphate, ammonium nitrate, etc.
190
What is the definition of organic chemicals?
Carbon based molecules found in living organisms.
191
What are some exceptions of organic chemicals?
These carbon based molecules are found in living organisms but are considered inorganic:Carbon MonoxideCarbon DioxideCarbonatesHydrogen Carbonates
192
Is it possible to produce organic chemicals without use of living organisms?
Friedrich Wöhler has proven that you can artificially make urea in laboratory. As Urea is an organic matter, you can produce organic matter with inorganic matter without vital force.
193
Draw a diagram of ribose.
Ribose is a pentose sugar. It is a monosaccharide.
194
Draw a diagram of alpha glucose.
Glucose is a hexose sugar. It is a monosaccharide.
195
Draw a diagram of beta glucose.
Glucose is a hexose sugar. It is a monosaccharide.
196
How is sucrose created?
Sucrose is disaccharide of glucose and fructose.
197
What is the difference between pentose and hexose?
Pentose is a sugar made of 5 carbon atoms while a hexose sugar has 6 carbon atoms
198
What is an example of a disaccharide?
Sucrose, Maltose, Lactose
199
What is a polysaccharide?
A Polysaccharide is a carbohydrate of a chain of many sugars which are for example starch or cellulose.
200
What is a glycosidic bond?
Glycosidic bond is formed between sugar molecules.
201
Draw and label a molecular diagram of a generalized amino acid.
Each amino acid contains: R group, carboxylic acid group, amino group, hydrogen atom and carbon atom in the middle.
202
How do amino acids join together?
Two amino acids bond to form a dipeptide. Amino acids join together through peptide bonds. This is a condensation reaction meaning it forms water as a by product.
203
What is a carbohydrate?
carbohydrates are organic compounds that contain one or more simple sugars.
204
What is a protein?
Large organic compounds made of a polypeptide of amino acids arranged in a linear shape.
205
Draw a molecular diagram of a saturated fatty acid.
Saturated lipids are linear, meaning they have no double carbon-carbon bonds.
206
What are examples of lipids?
Triglycerides, phospholipids and steroids.
207
Is this a carbohydrate, lipid or protein?
This is triglyceride which is a lipid.
208
Is this a carbohydrate, lipid or protein?
This is a phospholipid which is a lipid.
209
Is this a carbohydrate, lipid or protein?
This is a steroid which is a lipid.
210
What are some functions of lipids?
Lipids are used for electrical insulation, energy storage, plasma membrane (phospholipid and cholesterol) and thermal insulation.
211
Why are lipids surrounding our nerve cells?
Lipids a good electrical insulators as they do not conduct electricity.
212
What is metabolism?
Metabolism are the chemical reactions within the cell in its cytoplasm. It is the enzyme-catalyzed reactions in living organism.
213
What is anabolism?
Anabolism is the synthesis of small, simple molecules forming a complex compound. This includes the formation of macromolecules from monomers by condensation reaction.
214
What is catabolism?
Catabolism is the breakdown of complex compounds to small simple molecules. This includes the hydrolysis of macromolecules into monomers.
215
Draw a diagram of two sugars forming maltose.
Maltose is disaccharide created through the condensation of two alpha glucose which are bonded through a glycosidic bond.
216
How is sucrose formed?
Sucrose is a disaccharide formed through two monosaccharides, glucose and fructose.
217
How is lactose formed?
Lactose is a disaccharide formed through two monosaccharides, galactose and glucose.
218
How is maltose formed?
Maltose is formed through two alpha glucose.
219
What are some structures of starch?
Starch is polysaccharide of alpha glucose which comes in the form of amylose and amylopectin together.
220
What does amylose look like?
Amylose is a chain of alpha glucose bonds which is spiralled.
221
What does amylopectin look like?
Amylopectin is similarly to amylose made of alpha glucose but it branched.
222
How is cellulose formed?
Cellulose is polysaccharide made of a chain of beta glucose. It serves as a material to form plant cell walls.
223
What does glycogen look like and what is it used for?
Glycogen is very similar to amylopectin and is therefore made of alpha glucose. It is more branched. It serves as an energy source in human liver and muscles.
224
What is the difference between a saturated and unsaturated fatty acid?
Unsaturated fatty acids have double carbon-carbon bonds. This makes them bend.
225
What is the difference between monounsaturated and polyunsaturated fatty acids?
Monounsaturated fatty acids only have one double carbon-carbon bond. Polyunsaturated fatty acids have 2 or more double carbon-carbon bonds.
226
What kind of carbohydrates are cis and trans associated with?
Cis and trans are structures of unsaturated fatty acids.
227
Draw a molecular diagram of a cis unsaturated fatty acid
Cis resembles a C meaning that it curves back.
228
Draw a molecular diagram of a trans unsaturated fatty acid.
Trans is a nonpolar molecule, this makes the fatty acid a kink but stay relatively linear
229
How is triglyceride formed?
Triglyceride is formed through 3 fatty acids and a glycerol. The fatty acids attach themselves through condensation reaction which gives water as a byproduct
230
Explain how to find out your BMI
1. Measure your mass with a scale in kg2.Measure your height with a tape in meters 3. Divide your mass by your height squared=> BMI = weight/ (height)^2
231
Distinguish the differences of using lipids and carbohydrates as an energy source.
Lipids are more suitable for long term energy storage. Carbohydrates are more suitable for short term energy storage.
Lipids release double the amount of energy with the same amount of grams as carbohydrates. Carbohydrates release much less energy copared to lipids.
Lipids are stored in specialized cells such as triglycerides in adipose. Carbohydrates are stored in muscle tissues and the liver. This makes lipids more readily stored than carbohydrates.
Lipids take longer to break down. Glycogen is easier and faster to break down into glucose.
232
How can trans fats and saturated fatty acids affect our health?
There is a high correlation that a high intake of trans fats and saturated fatty acids. This is due to the fact that trans fats and saturated fatty acids can stack on each other and clot up blood vessels.
233
What are biological proteins composed of?
Biological proteins are made up of 20 different types of amino acids.
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Where do our cells get the amino acids?
Amino acids can be found through our diet and nutrients. Some amino acids can also be synthesized by human cells.
235
How are amino acids considered polar or nonpolar?
Whether amino acids are polar or nonpolar depends on their variable group (R group).Polar makes them hydrophilic.Non Polar makes them hydrophobic.
236
How does the polarity of an amino acid affect enzyme solubility?
The outer layer of an enzyme contains polar (hydrophilic) amino acids. This helps to make the enzyme soluble.
237
How does the polarity of an amino acid affect membrane proteins?
The inner pore of a membrane channel will contain polar amino acids, while the amino acids in contact with the lipid bilayer will be nonpolar. This keeps the protein from floating away.
238
How does the polarity of an amino acid affect proteins stability?
The inner layer of proteins will contain many non polar amino acids that help to stabilize the shape of a soluble protein.
239
Where do most organisms assemble their proteins from?
Most organisms have proteins that consist of the same 20 amino acids.There are a few exceptions that are likely to come from distant evolutionary relatives.
240
How do amino acids link together?
Amino acids link through condensation reaction, forming a peptide bond to make a dipeptide or polypeptide.
241
How are amino acids joined together in cells?
In cells, amino acids are joined by free ribosomes or by ribosomes attached to the RER.
242
What is the significance of the sequence of amino acids in polypeptides in living organisms?
The sequence of amino acids in polypeptides are codes for the genes.
243
What is the primary structure of protein structure?
Primary structure is a sequence of amino acids. The molecule is called a polypeptide.
244
What is the secondary structure of protein structure?
Secondary structure is the folding of the polypeptide to a combination of spiralled alpha helices and pleated beta sheets. They are held together by hydrogen bonds.
245
What is the tertiary structure of protein structure?
Tertiary structure is the chain folding into a specific 3D structure. The structure is held together by a number of different kinds of bonds.
246
What is the quaternary structure of protein structure?
A quaternary structure does not always occur.This occurs when two or more proteins in tertiary structure are bonded together to make 1 molecule.
247
What does the quaternary structure involve to form a conjugated protein?
To form a conjugated protein, the quaternary structure involves the binding of a prosthetic group.
248
What is the difference between fibrous proteins and globular proteins?
Fibrous proteins such as keratin which is found in hair is linear. While globular proteins such as pepsin are round.Fibrous proteins such are Keratin are insoluble. Other, globular proteins such as pepsin are soluble in waterFibrous proteins are less sensitive to changes in temperature and pH. Globular proteins are more sensitive. Fibrous proteins perform structural roles. Globular proteins act as catalysts.
249
What is proteome?
Proteome is the sum of all the proteins in one biological individual. This differs and is unique for every individual as we do not make the same amount of proteins.
250
What is the role of rubisco?
Rubisco is the enzyme that catalyzes carbon fixation in green plants. This is a key event in photosynthesis.
251
What is the role of insulin?
Insulin is hormone involved in the regulation of blood glucose concentration. It is composed of 2 peptides chains and totalling 51 amino acids.
252
What is the role of immunoglobulins?
Immunoglobulins act as antibodies which are large Y-shaped proteins that are used by the immune system to identify and neutralize foreign objects such as bacteria and viruses.
253
Are immunoglobulins fibrous or globular?
Immunoglobulins are globular.
254
What is the role of collagen?
Collagen is composed of three interwoven polypeptide chains, and is found in fibrous tissues such as tendons, ligaments, skin, bones and blood vessels. It serves to help our structure and support body tissues.
255
Is collagen fibrous or globular?
Collagen is fibrous.
256
What is an enzyme?
An enzyme is a biological catalyst which speeds up te rate of reactions.
257
What is an active side?
All enzymes have an active side whose shape is complementary to the substrate molecule(s).Enzymes are specific meaning that they can only speed the reaction of a specific substrate.
258
How do enzymes work?
1. Enzymes are shaped complementary to a substrate.2.Substrate moves into the enzyme and locks in. 3.An enzyme substrate complex is formed.4.A chemical reaction happens. The substrate is turned into products. Enzyme may act as catabolic or anabolic. 5. Products move out of enzyme 6. Enzyme is ready to accept another substrate molecule
259
Explain enzyme-substrate specificity.
Enzymes' active side and substrates have complementary shapes, so that the substrate fits into the enzyme like a key. This is called a lock and key model of enzyme action.A different kind of substrate cannot fit as the shape needs to fit perfectly. This makes enzymes specific. They are specific in order to make different products that the protein is assigned to.
260
If an enzyme is a protein, is it fibrous and globular?
Enzymes are globular proteins.
261
What happens to an enzyme when in extreme pHs or high temperatures?
The enzyme will be denatured. Denaturing refers to a permanent structural change in a protein that results in a loss of its properties Denaturing causes a change of shape of the active side of the enzyme which means it will not function anymore.
262
Draw a graph to show the expected effects of temperature on enzymes.
As temperature increases, relative activity increases until the enzymes is denatured where it will rapidly fall.
263
Draw a graph to show the expected effects of pH on enzymes.
As pH increases towards its optimum pH, relative activity increases. As pH increases away from its optimum pH, activity decreases.
264
Draw a graph to show the expected effects of substrate concentration on enzymes.
As concentration increases, activity increases to its point of saturation. Beyond the point of saturation, the increase in concentration remains constant.
265
Explain the effects of temperature on enzymes
As temperature increases, increases due to collision theory. As higher temperatures cause more movement, collisions occur more frequently. As temperature increases beyond the optimum temperature, the enzyme will denature causing activity to slow down rapidly.
266
Explain the effects of pH on enzymes
As the pH increases, enzymes are closer to their optimum pH where they work most efficiently. As pH increases beyond the optimum pH, the enzyme slowly starts to denature, slowing the activity.
267
Explain the effects of substrate concentration on enzymes.
When substrate concentration increases, collision frequency increases as there are more substrates enzymes can react with. After reaching point of saturation, activity can no longer be increase regardless of increase in substrates, as all enzymes are bound and reacting at maximum rate
268
What are immobilized enzymes?
Immobilized enzymes are enzymes which are restricted from movement and are in a fixed space.
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How are immobilized enzymes used in industry of production?
Immobilized enzymes are used in many industries. 1. Production of lactose free milk by having the enzyme lactase.2. Production of sodas where glucose isomerase is used to break glucose to fructose to make the drinks sweeter3. Production of fruit juice to break down pectin which makes it cloudy with the enzyme pectinase. 4. Biological washing powder contains protease, amylases and lipases. This makes it effective at breaking down food stains in low temperature that saves household costs.
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How is lactase used in the production of lactose free milk?
Lactase breaks down lactose into glucose and galactose This creates lactose free milk which can be enjoyed by consumers around the world, regardless of whether they are lactose intolerant or not.
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Outline advantages of lactose-free milk production
1. Allows people who are lactose intolerant to consume milk products. 2. It makes the milk taste sweeter, because glucose and galactose taster sweeter than lactose. This is good for smoothies and milk shakes. 3. Glucose and galactose are more soluble, making milk smoother and ice cream less crystallized. 4. It reduces production time for yogurt and cheese, as glucose and galactose are quicker to ferment than lactose.
272
What is the name of the structure of DNA?
DNA consists of many nucleotides. This is called a polynucleotide.
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How are DNA polynucleotide monomers linked?
DNA polynucleotide monomers are linked together by covalent bonds into single strand DNA polymers.
274
Draw a labelled diagram of single DNA Nucleotide.
Composed of deoxyribose sugar, nitrogenous bases and phosphorus group.
275
What are the 4 different nitrogenous bases for DNA?
A - Adenine G - GuanineT - Thymine C - Cytosine (Always go to chemistry)
276
What nitrogenous base is complementary to Adenine?
Adenine is complementary to Thymine. Double Hydrogen Bond.
277
What nitrogenous base is complementary to Cytosine?
Cytosine is complementary to Guanine. Triple Hydrogen Bond.
278
What are the base pairing rules?
Adenine double bond ThymineCytosine triple bond Guanine
279
Which nitrogenous bases are Purines?
Adenine and Guanine are purines.
280
Which nitrogenous bases are pyrimidine?
Thymine and Cytosine are pyrimidine.
281
Draw a structure of DNA with 6 DNA nucleotides.
DNA strands are antiparallel to form a double helix. Include: - Sugar phosphate backbone - complementary base pairs - Hydrogen bases between bases of two strands (dotted line)
282
What is the general structure of a DNA polynucleotide?
a DNA polynucleotide is a double stranded helix. The DNA strands are antiparallel linked by hydrogen bonds between the complementary nitrogenous base pairs.
283
Describe the structure of RNA.
RNA is a polynucleotide. RNA nucleotide monomers are linked together by covalent bonds into single stranded DNA polymers.
284
What are RNA nucleotides composed of?
RNA nucleotides are composed of ribose, one sugar phosphate group and a nitrogenous base.
285
What are the RNA complementary base pairing rules?
Adenine and Uracil Cytosine and Guanine
286
Draw a labelled RNA polynucleotide
Include sugar phosphate backbone.
287
Compare the structures of DNA and RNA
Similarities:
* Both have sugar phosphate groups
* Both have nitrogenous bases
* Both have pentose sugars
* Both are poly nucleotides
* Both have covalent bonds
* Both have sugar phosphate backbones
* Both have Adenine and Guanine as purines
* Both store genetic information
Differences:
* DNA has deoxyribose. RNA has ribose
* DNA is a double helix and is therfore double stranded. RNA is single stranded DNA must have hydrogen bonds between the nitrogen bases. RNA is mainly covalently bonded and only occasionally has hydrogen bonds.
* DNA has Thymine and Cytosine as pyrimidines. RNA has Uracil and Cytosine as pyrimidines.
* DNA has an anti-parallel structure. RNA with only one strand has only one direction. 5' to 3'
288
How does the discovery of the DNA structure give insight into the mechanism of DNA replication?
As we know that DNA has a double stranded structure, and is defined by their sequence in order to store genetic information, we can deduct that a replication of a strand can be created through the information of the complementary strand.
289
Outline the protocol of the Hershey and Chase experiment.
1. Phages were attached to a bacterial cell. 2. The DNA is transferred through injection into the bacterial cell.3. Phage had normal DNA but was covered in radioactive protein coat4. Phages were attached to bacterial cell, and DNA was transferred and reproduced. Next generation was not radioactive. 5. Phage had radioactive DNA covered in normal protein coat.6. Next generation was radioactive.
290
What is a phage?
A phage is a type of virus that infects bacteria. Phages are made from DNA covered with a coat of protein.
291
From the Hershey and Chase experiment, what can we deduce?
From the experiment we can deduce that protein does not pass on genetic information or even contain such.From the experiment we can also deduce that DNA is inherited by the next generation. Therefore, DNA stores genetic material that is information needed for the next generation
292
What can we deduce from the X-ray crystallography?
From the crystallography we can find that strands over lap like intersections and therefore DNA should be a double stranded helix.
293
What does the DNA Helicase do?
In DNA replication, DNA Helicase unzips the double stranded DNA helix by breaking apart the hydrogen bonds.
294
What does DNA gyrase do?
DNA gyrase releases tension from the DNA double helix. It does this by breaking both strands and unwinding the strand by 2 coils and then fusing the DNA strands back together.
295
What does DNA polymerase I do?
DNA polymerase I replaces the RNA strand with a DNA strand.
296
What does DNA polymerase III do?
DNA polymerase builds complementary DNA strands (sugar phosphate backbone)
297
What do single stranded binding proteins do?
Single stranded binding proteins prevent the single DNA strands from sticking back together.
298
What does DNA primase do?
DNA primase inserts a piece of RNA to the single strand
299
What are Okazaki fragments?
Are the sections of DNA on the lagging strand that need to be connected
300
What does dNTP do?
DNA polymerase II uses dNTP (Deoxynucleotide triphosphate) to build a new complementary strand of DNA (connecting the Okazaki fragments). Two phosphate groups are removed
301
What does DNA ligase do?
DNA ligase is responsible for joining the Okazaki fragments to create a continuous strand.
302
Name at least 5 functions in DNA replication.
○ Helicase ○ DNA gyrase ○ single strand binding proteins ○ DNA primase ○ DNA polymerases I ○ DNA polymerases III ○ Okazaki fragments ○ deoxynucleoside triphosphates (dNTPs) - also known as 'free nucleotides'
303
In which direction does DNA replication occur?
DNA replication occurs in a 5' to 3' direction because DNA polymerase 3 only adds nucleotides to the 3' end of the primer.
304
Outline the process of DNA replication (on the leading strand)
1. DNA helicase unzips the double stranded DNA helix by breaking the hydrogen bonds 2. The single stranded binding proteins attach themselves to each strand to prevent them from sticking back together. 3. DNA Primase adds a new RNA strand to the single strand.4. DNA polymerase III builds a new complementary DNA strand. The existing strand is used as a template using the complementary base pairing rules5. DNA polymerase I replaces the RNA primer with a short DNA strand. On the leading strand DNA polymerase III can build a complementary DNA strand continuously.
305
Outline the process of DNA replication (on the lagging strand)
1. On lagging strand the new complementary DNA strand must be built in sections called Okazaki fragments due to the fact that the DNA polymerase III only goes in one direction, 5' to 3'2. DNA ligase is required to join together the Okazaki fragments. On the lagging strand DNA polymerase III has to work discontinuously because it only works in one direction from 5' to 3'
306
When does DNA replication occur in eukaryotic chromosomes?
DNA replication initiates at many points in eukaryotic chromosomes. This is because eukaryotic genomes are usually larger than prokaryotic genomes. So DNA is replicated at many points simultaneously in order to limit the time required for DNA replication to occur.
307
What are the sites called where DNA unwinding and initiation of replication occurs?
These sites are called origins of replication and form replication bubbles.As replication bubbles expand they eventually fuse together. Two generate two separate semi conservative double strands of DNA
308
Is DNA replication conservative, semi-conservative or dispersive?
DNA replication is semiconservative. One strand will form from the original DNA strands. One strand will be newly synthesized.
309
Outline the protocol of Meselson and Stahl's DNA replication experiments
Meselson and Stahl grew an E.Coli bacteria in a medium containing N15 Nitrogen atoms. After several generations all of the bacteria contained heavy DNA with two strands made from N15.Then the E.Coli bacteria was transferred into a medium containing N14 nitrogen Scientists allowed bacteria to complete 1 cell division by binary fission. They then took samples of the cells and tested the DNA in a centrifuge to measure its weight. The bacteria then was allowed to complete several more replications by binary fission. Each time DNA was taken and measured in a centrifuge.
310
What can we conclude from Meselson and Stahl's experiment?
From Melson and Stahl's we can deduct that DNA replication is semi conservative as there is as DNA is always semi-transferred and semi conserved into the new generation.
311
What is the significance of the complementary base pairing rules to determine
DNA polymerase uses the complementary base pairing rules to determine the sequence of nucleotides as it builds a new strand of DNA. This ensures that the two daughter cells produced by mitosis are genetically identical
312
What is Taq polymerase?
Taq polymerase is a thermo-stable DNA polymerase enzyme. This is enzyme is found from the heat loving bacteria, thus does not denature at extreme temperatures.
313
What does Taq polymerase do?
Taq polymerase performs the same role as DNA polymerase by producing several copies of of DNA during polymerase chain reaction. In order to artificially replicate human DNA.
314
What is the relationship between one gene and one polypeptide?
One gene holds information to make one polypeptide. (A gene is a section of the DNA)
315
Outline the process of transcription.
Process takes place inside the nucleus1. RNA polymerase will attach it self to the promoter site of the DNA.2. RNA polymerase unwinds the DNA by breaking hydrogen bonds. This creates a transcription bubble.3. RNA polymerase will build a new strand using complementary base pairing rules to pair RNA nucleotides along the anti sense strand. 4. RNA polymerase reaches terminator where transcription is completed. 5. RNA polymerase breaks away from DNA6. DNA double helix rewinds and mRNA is released
316
What are the three types of RNA?
mRNA (messenger = transcription)tRNA (transfer = translation)rRNA (ribosome = translation)
317
Outline the process of translation. (SL)
1. Small ribosome sub-unit attaches itself to mRNA strand. 2. mRNA is made of codons which is a sequence of 3 consecutive RNA bases. tRNA has anti codons which is also made of 3 consecutive RNA bases. A tRNA molecule always corresponds to a specific amino acid. 3. Ribosomes will read the codons on the mRNA and using complementary base pairing rules, pair appropriate tRNA molecules. 4. The ribosome works its way along the mRNA in direction of 5' to 3'. Until it finished building the polypeptide chain.
318
Where does translation occur?
In a cell's cytoplasm
319
When does translation occur in the cell cycle?
G1 and G2 Phase
320
Why does translation happen?
Translation happens in order to make polypeptides for protein synthesis.
321
What is the role of a ribosome?
The role of a ribosome is to read the base sequence of the mRNA and use this information to build a polypeptide.
322
What is the role of mRNA?
The role of mRNA is to hold genetic information from the nucleus to the ribosome.
323
What is the role of tRNA?
The role of tRNA is to bring specific amino acids to the ribosomes for protein synthesis.
324
How does amino acid sequence of polypeptide is determined by base sequence of mRNA?
As the sequence of mRNA is composed of codons it directly corresponds to an anti codon with its specific amino acid that is always the same for the specific code. Thus, the amino acid sequence is determined by the genetic code.
325
Does the amino acid correspond to mRNA or tRNA?
Amino acids are determined by the mRNA and not the tRNA.
326
What is GMO?
GMO means genetically modified organisms.
327
What is an example of the universality of the genetic code allowed gene transfer between species?
The production of human insulin in bacteria is a demonstration as to how bacteria can be genetically modified through transfer of gene. This is done by replacing a gene for human insulin into a bacterial plasmid, which in the bacterial organism will produce human insulin to treat diabetics.
328
What happens after the process of transcription in eukaryotic cells?
In eukaryotic cells, the mRNA has to be modified after transcription.
329
How can eukaryotic RNA form into a mature mRNA?
Eukarytoic RNA has to remove introns.
330
Why is splicing important?
mRNA splicing has to function to remove unnecessary non-coding regions before translation. Introns allow cells to make a variety of slightly different polypeptides from the same gene. Sometimes an intron can be included in the mRNA. This will produce a slightly different polypeptide. Thus a slightly modified protein.
331
What is an example of a non coding region with a function?
A promoter site is an example of a non-coding DNA with a function.
332
When does specialization occur?
Cell specialization occurs through a process of differentiation where genes are swicthed off.
333
What is a major role in affecting cell specialization?
The environment plays a major role in affecting whether genes are switched off or on. It has an effect of the gene expression.
334
What is phenotypic plasticity?
It is the ability of an organism to develop in different ways according to its environment.
335
What is a nucleosome?
One nucleosome is made of 8 histone proteins, with DNA wrapped around the outside. Only eukaryotic cells have nucleosomes.
336
What is the function of a nucleosome?
Nucleosomes protect DNA from damageThey allow long lengths of DNA to be supercoiled for mobility of mitosis.Nucleosomes help to regulate DNA transcription.
337
How do nucleosomes act to regulate DNA transcription?
While a DNA strand is wrapped around a histone protein, in a nucleosome, the enzyme RNA polymerase cannot unwrap the DNA double helix for transcription to occur. Some parts of a cell's DNA is permanently wrapped into nucleosomes that permanently switch off the gene.
338
Do prokaryotic cells have nucleosomes?
No. Prokaryotic cells have naked DNA meaning that they do not have histone proteins to form nucleosomes.
339
How can gene expression be regulated?
Through proteins, gene expression can be regulated and therefore temporarily regulated. This happens when proteins bind to specific base sequences in the DNA, such a promoting protein or a blocking protein on the operator site.
340
Outline the structure of a ribosome.
Ribosomes are made of rRNA and proteins.It is composed of 2 sub-units: a large sub-unit and a small sub-unit. It consists of 3 binding sites for tRNA.It has one binding site for mRNA.
341
What is the structure of a tRNA?
A tRNA molecule is a polynucleotide chain. It is folded back to form a region of double helix, according to RNA complementary base pairing rule.It contains 3 loops.It contains an anti-codon with 3 RNA bases.It has a binding site for an amino acid.
342
How are tRNA molecules charged?
tRNA molecule has to be linked to a specific amino acid through a tRNA - activating enzyme. 1. Specific amino acid binds to active side of a tRNA-activating enzyme.2. ATP binds to active site of the enzyme to provide energy stored in the 3 phosphate groups.3. 2 of the phosphate groups break away which releases energy captured by the amino acid.4. A specific tRNA molecule binds to the active site of tRNA activating enzyme which active site has to be complementary to the anti codon of tRNA. 5. High energy bond between the amino acid and tRNA molecule is formed which activates the tRNA molecule. The energy carried by the tRNA molecule will be used for to form a peptide bond. 6. The tRNA molecules leaves the enzyme to find a ribosome
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What is the tRNA activating enzyme an example of?
tRNA activating enzyme is an example of enzyme-substrate specificity
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What is the first process of translation?
Initiation 1. The small ribosome sub-unit binds to the mRNA 2. The complementary anti-codon of the tRNA molecule binds to with the start codon at the P-Site3. The large sub-unit of the ribosome binds to the mRNA.
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What is the second process of translation?
Elongation 1. A second tRNA molecule moves into the A-site2. A peptide bond forms between the two amino acids held in A Site and P site.
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What is the third process of translation?
Translocation1. The ribosome moves 3 nucleotides along the mRNA strand.2. the first tRNA molecule moves into E-site and exits the ribosome 3. A-Site is available for a new tRNA molecule.
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What is the fourth process of translation?
Termination1. Eventually the ribosome will reach the stop codon 2. The ribosome breaks apart into two sub-units Polypeptide is complete.
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In which direction does translation occur?
5' to 3' direction
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What is the difference of the function of free ribosome and ribosome on the RER?
Free ribosome: make protein primarily for inside the cell.Ribosome on RER: make protein for export out of the cell or for lysosome (i.e. hormones such as insulin)
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Is translation in eurkayrotic cells as quick as in prokaryotic cells?
No. Translation in prokaryotes can occur immediately after transcription due to the absence of the nuclear membrane.
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What is a polysome?
A polysome is formed when several free ribosome attach themselves to the same strand of mRNA. The advantage of this is that it produces the same amount of polypeptides in a shorter amount of time.
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What kind of bonds maintain the tertiary and quaternary structure of protein?
Hydrogen BondsDisulfide bridgesIonic BondsHydrophobic Interactions (Inter molecular Forces)
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What is a genome?
Genome is the whole of the genetic information of an organism.
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What is a gene?
Gene is a heritable factor that controls a specific characteristic.
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What is an allele?
An allele is one of a number of different version of a gene
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What is the Human Genome Project?
The HGP is an international research effort to sequence , map and understand all the genes of members of species, homeosapiens. 18 different countries were involved. It began in 1990 and finished in 2003
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What importance does the Human Genome Project have? Why do we need the sequencing of the complete human genome?
By being able to read nature's complete genetic blueprint of a human being:- to learn about the causes of genetic diseases and thus find cures and treatments.- to discover more about how different people are related to each other and to other species /evolutionary relationships - to understand more about the aging process
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What is gene mutation?
Gene mutation is natural process that causes changes in the DNA sequence caused by a mutagen. The change in DNA sequence causes a change in mRNA, and amino acid sequence and thus produce new alleles.
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What is mutagen?
Mutagen is a physical or chemical factor that causes a change in DNA base sequence.
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What are the consequences of mutations?
There negative effects of mutations such as cancer. Positive effects of mutation are the creation of new alleles for adaption. Sometimes there are no consequences at all as the it codes for the same amino acid.
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What is a consequence of a base substitution mutation?
Base substitution mutation is a change of a single base in a sequence of DNA. Example: Sickle Cell Anemia Base substitution mutation: - the sequence of nucleotide bases in DNA codes for the sequence of amino acids in proteins- DNA is transcribed into mRNA, which is translated into amino acids of protein- normal (ß chain) hemoglobin gene / DNA produces - normal (ß chain) hemoglobin protein / amino acidssubstitution= the replacement of one (or more) nucleotide base with another- caused by a copying mistake during DNA replicationas a result of a mutagen / X-rays / chemical / UV radiation / other mutagen- mutation in normal (ß chain) hemoglobin gene alters the sequence of nucleotide bases- normal nucleotide sequence = CTC altered to CACresulting in altered mRNA (GAG to GUG) during transcription- resulting in altered sequence of amino acids in (ß chain) hemoglobin protein (glutamic acid to valine) during translation- causing red blood cells to change shape / sickle under low oxygen conditions- causing sickle cells anemia when two copies of the mutated gene are inherited- producing a sickle cell carrier when one copy of the mutated gene is inherited- sickle cells anemia reduces oxygen flow to organs, leading to their deterioration
362
Compare eukaryotic and prokaryotic chromosomes
Prokaryotes have one chromosome consisting of a circular DNA molecule. Eukaryotes have chromosomes that have linear DNA molecules.Prokaryotic DNA is naked. Eukaryotic DNA molecules are wrapped around histone proteins. The circular prokaryotic chromosome contains all genes.. Eukaryotes have different chromosomes with different genes.Prokaryotes sometimes have plasmids. Eukaryotes do not.
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What are homologous chromosomes?
Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles.
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What are diploid nuclei?
A diploid nucleus contain two copies of each homologous chromosome/ have pairs of homologous chromosome/ two chromosomes of each type. number of chromosomes = 2N
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What are haploid nuclei?
A haploid nuclei has one chromosome of each homologous chromosome. number of chromosomes = N
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What was used to establish the length of DNA molecules?
Due to developments in scientific research, improvements were made in their techniques that included using autoradiography to establish the length of DNA molecules in chromosomes as they discovered specific substances located in cells/tissues.
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What does the number of chromosomes indicate?
Number of chromosomes is a characteristic feature of members of a species.
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How are genders determined on a karyogram?
Gender is determined by sex chromosomes.
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What are autosomal chromosomes?
Autosomal chromosomes are chromosomes that determine the sex. (1st to 22nd Pair)
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What can we deduce on a karyogram of an unborn baby?
We can identify the gender.We can identify chromosomal abnormalities in health.
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What is a karyogram?
Karyograms show the chromosomes of an organism in homologous pairs of decreasing length
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How can you diagnose Down syndrome and what its syndromes?
If there are three copies of chromosome 21 instead of two, the individual as down syndrome. Some of the component features of the syndrome are hearing loss, heart and vision disorder. Mental and growth retardation are also very common.
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Outline Cairns technique for measuring the length of DNA molecules.
- radioactively labelled chromosomes of the DNA by growing them in a medium containing thymidine- Using an enzyme cell walls were digested so that cells could release their DNA- a thin film of photographic emulsion was applied to the membrane so that when DNA decayed, it reacted with the film - Dark grains are seen where DNA decayed which indicates the position.
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What are Pan troglodytes?
Chimpanzees
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What are Canis familiaris
Dogs
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What are the methods to collect cells from embryo for karyotyping?
Amniocentesis and chorionic villus sampling are two methods to collect the amniotic fluid.
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What is Meiosis?
Meiosis is one of the two ways in which the nucleus of a eukaryotic cell can divide. (The other is Mitosis)
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Why use Meiosis and not Mitosis?
Meiosis allows the halving of chromosome numbers that allow sexual life cycle with fusion of gametes. This allows genetic variation.
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When does Meiosis occur?
Meiosis can happen at any stage during sexual life cycle, but in animals it happens during the process of creating the gametes. Body cells are diploid.
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List all stages of Meisosis
1. Interphase2. Prophase I3. Metaphase I4. Anaphase I5. Telophase I/Cytokinesis6. Prophase II7. Metaphase II8. Anaphase II9. Telophase II
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What happens before Meiosis?
During the last stage of interface, DNA is replicated.
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What happens during Prophase I (Meiosis)?
1. Nuclear membrane breaks down2. Homologous chromosomes pair up to form bivalents/tetrads.3. Homologous chromosomes are held together by points called chiasma4. Homologous chromosomes undergo a process called synapsis whereby sections of DNA are exchanged between homologous chromosomes.5. Crossing over of genetic material between non-sister chromatids can occur at these points, resulting in new gene combinations (recombination)
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What happens during Metaphase I?
1. Centrioles form on either side of the cell2. Microtubulos grow and attach themselves to the centromeres of homologous tetrads3. Homologous tetrads line up along the equator
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What happens during Anaphase I?
1. Homologous chromosomes split apart and move to opposite poles
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What happens during Telophase I?
1. Nuclear membrane reforms 2. Centrioles and microtubules break down 3. Cell splits into two haploid daughter cells as cytokinesis occurs.
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What happens during Prophase II?
1. Nuclear membrane breaks down
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What happens during Metaphase II?
1. Chromosomes line up along the equator of the cell 2. Spindle fibres reform and reconnect to the chromosomes
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What happens during Anaphase II?
1. Spindle fibers shorten and pull sister chromatids apart as they move to opposite poles.
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What happens during Telophase II?
1. The cell splits in two as cytokinesis happens concurrently.
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What is the result of Meiosis?
Because sister chromatids may no longer be genetically identical as a result of potential recombination, the process of meiosis results in the formation of four genetically distinct haploid daughter cells.
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Outline the process of crossing over.
Crossing over involves the exchange of segments of DNA between homologous chromosomes.During synapsis in prophase I, homologous chromosomes pair up to form bivalents/tetrads. Portions of non-sister chromatids overlap. The positions in which they are attached are called chiasma.The chromatids break at chiasmata, reattach to new sister chromatids in a system of reciprocal exchange. The new combinations are known as recombinants.
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How does meiosis produce genetic variation?
1. Random orientation of bivalents/Independent Assortment: Bivalents line up along the equator in metaphase I. This means that chromosomes assort independently into two daughter cells during anaphase I. Chromosomes align along the equator independently during metaphase II. This means that chromatids assort independently into daughter cells during anaphase II2. Chiasma formation:During Prophase I, genetic exchange occurs between homologous chromosome during synapsis. This creates chromosomes with new combinations of alleles. 3. Offspring of sexual reproduction have two parents (Fusion of gametes)
393
What are the genetic basis for Down's syndrome to occur?
Non-disjunction can cause Down syndrome.The failure of the chromosomes to separate may either occur via:
* Failure of homologues to separate during Anaphase I (resulting in four affected daughter cells)
* Failure of sister chromatids to separate during Anaphase II (resulting in two affected daughter cells)
Thus, both of the chromosomes move to one pole while none to the other.This results the gametes, sperms or eggs, to have incorrect number of chromosomes.Down syndrome (trisomy 21) is an example. The person would have three homologous chromosomes #21.
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Explain how meiosis results in an effectively infinite genetic variety in gametes
independent assortment: - variety produced by recombination of maternal and paternal chromosomes- for each pair of homologous chromosomes, maternal and paternal chromosomes assort to daughter cells randomly- possible arrangements of chromosomes in haploid daughter cells = (2)nth, where n = number of homologous pairscrossing over: - variety produced by recombination within individual chromosomes- during synapsis, prophase I, homologous chromosomes pair forming bivalents- portions of non-sister chromatids overlap, break at chiasmata, reattach to new chromatid in a system of reciprocal exchange- new combinations known as recombinants
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What is a phenotype?
Phenotype is an observable trait or characteristic.
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What is a genotype?
Genotype is an organism's genetic make up
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What is an allele?
An allele is a version of a gene.
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What is a dominant allele?
An allele which determines the phenotype of a heterozygote.
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What is a recessive allele?
An allele which can only influence the phenotype of a homozygote.
400
What is the locus?
A position in a chromosome.
401
What is homozygous?
An organism is homozygous when it has two identical alleles of the same gene.
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What is heterozygous?
An organism is heterozygous when it has two different alleles of the same gene.
403
When a test cross is performed what happens?
Testing a suspected heterozygote by crossing it with a known homozygous recessive.
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What is a monohybrid cross?
A monohybrid cross determines the allele combinations of offspring for one particular gene only (HL students may refer to topic 10.2 for dihybrid crosses)
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A parent organism of unknown genotype is mated in a test cross. Half of the offspring have the same phenotype as the parent. What can be concluded from this result?
The parent of unknown genotype is heterozygous.
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The gene for brown hair is B and the gene for blond hair is ba) Write down the genotype of a woman who is heterozygous for brown hair.b) Write down the genotype of a man who has blond hair.c) Work out the possible offspring of these two people.
a) Bbb) bbc) 50% Brown hair & 50% blond hair
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What is the use of test cross?
A genetic cross is a means of determining the genetic characteristics of potential offspring based on the genetic characteristics of the prospective parents.By test crossing we can determine the parent's unknown genotype.
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What is codominance?
Codominance means that two different alleles both affect the phenotype of a heterozygote.
409
How many alleles can a gene have?
A gene can have multiple alleles that means more than 2 versions of the same gene.
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What is an example of codominance and multiple alleles?
ABO blood groups have codominant alleles as well as more than 2 alleles for the same gene. (Recessive allele is i which does not produce glycoprotein. Phenotype = Blood group O)
411
What is sex linkage?
Sex linkage occurs when a gene is located on one the sex chromosomes (chromosome #23)
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What are examples of sex linkage?
Red Green Color Blindness & Hemophilia are both examples of X-linked recessive conditionsThe gene loci for these conditions are found on the non-homologous region of the X chromosome (they are not present of the Y chromosome)As males only have one allele for this gene they cannot be a carrier for the condition This means they have a higher frequency of being recessive and expressing the traitMales will always inherit an X-linked recessive condition from their motherFemales will only inherit an X-linked recessive condition if they receive a recessive allele from both parents
413
Can males be both homozygous and heterozygous with respect to sex-linked genes?
No. As human females have two X chromosomes (and therefore two alleles for any given X-linked gene), they can be either homozygous or heterozygousMales only have one X chromosome (and therefore only one allele) and are hemizygous
414
Explain that female carriers are heterozygous for X-linked recessive alleles
An individual with a recessive allele for a disease condition that is masked by a normal dominant allele is said to be a carrierCarriers are heterozygous and can potentially pass the trait on to the next generation, but do not suffer from the defective condition themselvesFemales can be carriers for X-linked recessive conditions because they have two X chromosomes - males (XY) cannot be carriersBecause a male only inherits an X chromosome from his mother, his chances of inheriting the disease condition from a carrier mother is greater
415
What is the cause of most genetic diseases?
Many genetic diseases in humans are caused due the recessive allele of autosomal genes, although some genetic diseases are due to dominant or codominant alleles.
416
What is cystic fibrosis?
• Autosomal disease • Recessive• C = healthy/ c = cystic fibrosis• Suffers produce a thick mucus in their lungs which gives them trouble breathing• No cure, no effective treatment.
417
What is Huntington's disease?
* Autosomal Dominant
* H = Huntington's disease h = healthy
* patients incur damage to nerve tissues, mental decline aged 30+
418
Explain why large sample sizes are necessary in genetics investigations
• Large sample sizes increases reliability of the data• Large sample sizes reduce the impact of random effects/ small sample sizes increases the impact of random effects
419
What is mutagen?
Mutagens a physical or chemical factor that causes DNA mutations • Physical (UV rays, gamma radiation, X-rays) • Chemical (polonium, radium, dioxins, carbon monoxide, uranium)
420
What are the consequences of radiation after a nuclear bomb?
• Higher rate of cancer among survivors • Blood disorders (e.g. Leukemia)• Down syndrome • Soil contamination
421
What is a dihybrid cross?
A dihybrid cross determines the allele combinations of offspring for two particular genes that are unlinked (not on the same chromosome)To work out gamete combinations remember FOIL:• First (AaBb = AB)• Outside (AaBb = Ab)• Inside (AaBb = aB)• Last (AaBb = ab)
422
Assuming that the flowers' dominant alleles are phenotypes for tall and purple. If there are two heterozygous tall purple flowers crossed, what is the probability of getting offspring with the same phenotype?
9/16
423
What is used to determine whether the difference between an observed and expected frequency distribution is statistically significant?
Chi squared/ X2Degrees of freedom are determined by the number of types of offsprings, minus one.
424
Explain how crossing over between non-sister chromatids of a homologous pair in prophase I can result in the exchange of alleles
* crossing over/chiasmata formed during prophase I of meiosis;
* pairing of homologous chromosomes/synapsis; chromatids break (at same point); (do not accept chromatids overlap)
* non-sister chromatids join up/swap/exchange alleles/parts;
* X-shaped structure formed / chiasmata are X-shaped structures;
* chiasma formed at position where crossing over occurred;
* chiasmata become visible when homologous chromosomes unpair;
* chiasma holds homologous chromosomes together (until anaphase
425
Draw a diagram of chiasma formed by crossing over
Recombinants formed by crossing over
426
Explain the relationship between Mendel's Law of Independent Assortment and Meiosis
Meiosis divides the chromosomes into groups of four. Each allele for one trait has a 50% chance of being passed on. But the two alleles combined make four different options, which makes the chances for these being passed on 25%.
427
State Mendel's Law of Independent Assortment
The alleles of two genes pass into gametes without influencing each other.
428
What is an autosomal linkage group?
When two genes are located on the same autosomal chromosome
429
What is polygenic inheritance?
When many genes control the same phenotype (or characteristics). A good example is skin colour.
430
What do phenotypes of polygenetic characteristic tend to show?
The phenotypes of polygenic characteristics tend to show continuous variation
431
Explain an example of a cross between two linked genes.
Unlinked genes assort independently in a dihybrid cross between heterozygotes, producing a 9:3:3:1 phenotypic ratio Linked genes, without crossing over, do not follow the expected 9:3:3:1 phenotypic ratio for a dihybrid cross between heterozygotes
* Instead the result will follow the 3:1 phenotypic ratio of a monohybrid cross, as the two linked genes are inherited together
* This means that all the offspring will produce parental phenotypes
Linked genes with crossing over produce recombinant phenotypes in numbers that reflect the distance between the linked genes
* distant genes will cross over more frequently, producing a higher percentage of recombinants
* genes that are close together will cross over less frequently, producing a lower percentage of recombinants
A test cross involving two linked genes, A and C: AaCc x aacc
* 80% of offspring are parental, either AaCc or aacc
* 20% of offspring are recombinant, Aacc or aaCc
* thus, the two genes are linked and are 20 cM apart on the same chromosome
432
Outline the process of polymerase chain reaction (PCR)?
1. DNA is collected and heated to a very high temperature to break the hydrogen bonds between the double stranded DNA. 2. When the mixture is then slightly cooled, DNA primers are inserted using DNA complementary base pairing rules that form hydrogen bonds.3. When the mixture heats up again, Taq polymerase i added to create a new complementary strand of DNA using free DNA nucleotides and the base pairing rules4. This process repeats several dozen times so that millions of copies are produced
433
What is the process of PCR (artificial DNA replication) called?
Amplification
434
During PCR, are small or larger amounts of DNA used?
Only minute/very small amount of DNA is needed to amplify.
435
What is used to separate proteins or fragments of DNA?
Gel electrophoresis is used to separate proteins or fragments of DNA according to size.
436
What is used for DNA profiling?
Amplification/PCR, restriction enzymes to cut the DNA, gel electrophoresis to separate the DNA fragments.
437
How does gel electrophoresis separate proteins or DNA fragments?
When DNA is in fragments, they can be placed into the gel.An electric field is applied which makes the molecules move to their opposite charge. The smallest fragments travel furthest towards positive charge. UV probe is used to make them visible.
438
What are the uses for DNA profiling?
Solving crimes, Identifying paternity & analyzing evolutionary relationships.
439
What is GMO?
Genetically modified organisms where gene transfer between specifies has been carried out.
440
What is an example of a technique used for gene transfer to bacteria?
Production of Human InsulinStep 1: Bacteria has plasmids that contain a small ring of naked DNA that can be copied and shared with other bacteria in order to share useful genesStep 2: Restriction enzymes are used to cut the plasmid DNA. Step 3: The gene for human insulin is inserted into the Plasmid. The sticky ends of the gene and the plasmid have to be complementary. DNA ligase sticks them together. The plasmid has now a recombinant DNA.Step 4: The plasmid is inserted back into the bacteria where it acts as a vector. Step 5: Under a suitable environment, the bacteria will quickly reproduce and be able to synthesize protein for human insulin due to the recombinant DNA.
441
Outline 2 examples of current uses of GMOs
Golden Rice: Was enriched with Vitamin A which helps improve the health of poor rural communities whose diet is dependent on rice but lack Vitamin A levels. However, may go against religious, cultural heritage and beliefs because the food is no longer pure. Poor communities may become dependent on the golden rice and not focus on a general improvement in their diet. Bt corn: Bt corn has increased resistance to attack from insects, farmers need to use less insecticide. This reduces the cost of farming as well as environmental contaminationBt corn plants have been genetically engineered to produce a toxic chemical that kills insects. This chemical is also present in the harvested crop. This may pose a threat to human health
442
Discuss potential benefits and possible harmful effects of genetic modification
MUST have examples:Benefits:• benefits include more specific (less random) breeding than with traditional methods• faster than traditional methods•some characteristics from other species are unlikely in the gene pool / selective breeding cannot produce desired phenotype•increased productivity of food production / less land required for production• less use of chemical (e.g. pesticides in Bt Corn)• food production possible in extreme conditions (Amflora - GM potatoes are cold/drought resistant)• less expensive drug preparation e.g. pharmaceuticals in milk• human insulin engineered so no allergic reactions• may cure genetic diseasesRisks:• Could have currently unknown harmful effects (e.g. toxin may cause allergic reactions in a percentage of the population)• Accidental release of transgenic organism into the environment may result in competition with native plant species• Possibility of cross pollination (if gene crosses the species barrier and is introduced to weeds, may have a hard time controlling weed growth)• Reduces genetic variation / biodiversity (corn borer may play a crucial role in local ecosystem)
443
What are clones?
Clones are a group of genetically identical organisms or a group of cells derived from a single parent cell
444
Does cloning only occur artificially?
No. Cloning can occur naturally for some animal species and many plants such as potatoes, garlic, onions and wild strawberries.
445
Outline 2 techniques for cloning
Cloning at embryo stage:Animals can be cloned at the embryo stage by breaking up the embryo into more than one group of cellsCloning at adult stage:using somatic-cell which are differentiated cell transfer
446
Outline the technique to clone adult animals
1. Remove a somatic cell (usually a skin cell) from the mouse that you want to clone. Obtain an egg cell from another organism2. Remove the nucleus from the egg cell using a harp pipette. The egg now contains no DNA which makes it enucleated 3. Remove the nucleus from the somatic cell using a sharp pipette4. The nucleus from the somatic cell is injected into the enucleated egg cell5. The cloned cell is treated with chemicals in order to stimulate it to begin cell division which makes a cloned embryo6. Implant the cloned embryo into the uterus of a surrogate organism. Once pregnancy is completed, the surrogate will give birth to the cloned organism
