Genetic Information, Variation And relationships Between Organisms (3.4) Flashcards
1
Q
What is a histone?
A
A protein which provides structural support for a chromosome
2
Q
Name 3 similarities and differences between DNA in prokaryotes and eukaryotes.
A
DNA in prokaryotes:
- circular DNA with no free ends
- relatively short
- not bound to histones
DNA in eukaryotes:
- linear DNA with two ends
- much longer
- tightly wrapped around histone proteins
3
Q
In which organelles, beside the nucleus, is DNA found in?
A
Mitochondria and chloroplasts
4
Q
DNA in chloroplasts and mitochondria is similar to the DNA found in _______.
A
Prokaryotes
5
Q
what is a histone?
A
Proteins which provide structural support for a chromosome
6
Q
What is a chromosome?
A
Linear DNA in the nucleus of eukaryotic cells.
7
Q
What is chromatin?
A
DNA that is wrapped and coiled around histone proteins.
8
Q
What is the function of DNA?
A
To store genetic information and codes for proteins
9
Q
what type of molecule is DNA?
A
Joint nucleotides forming a polymer
10
Q
What are nucleotides made up of?
A
Phosphate group, deoxyribose sugar, organic bases
11
Q
phosphate group + deoxyribose sugar=?
A
Sugar phosphate backbone
12
Q
What are the 4 bases
A
Adenine- thymine
Guanine-cytosine
13
Q
What is a polypeptide?
A
A polymer made from amino acids, joined together by peptide bonds.
14
Q
What does supercoiled mean?
A
The amount of twist on a DNA strand, which determines the amount of strain on it.
15
Q
What is a codon?
A
A DNA or RNA sequence of 3 nucleotides
16
Q
what is a gene?
A
A section of DNA that codes for certain characteristics
17
Q
What is an allele?
A
A version of a gene
18
Q
What is a loci?
A
Location of a gene on a chromosome
19
Q
What are sister chromatids?
A
Identical chromatids, formed by the DNA replication of a chromosome with both copies joined by a common centromere.
20
Q
What is an intron?
A
The non-coding sections of DNA which are spliced out of the mRNA sequence during transcription.
21
Q
Introns stay ___ the nucleus.
A
In
22
Q
What are exons?
A
The coding sections of genes which can be expresses as functional RNA or polypeptides.
23
Q
Exons _____ the nucleus.
A
Exit
24
Q
Genes are located on __________ and occupy specific positions on the chromosome known as its _____.
A
Chromosomes
Locus
25
Genes are made up of ________ and ____-_____ DNA
Coding
Non-coding
26
Exons are ______ during transcription an from the ___ that exits the nucleus and is expressed as the functional polypeptide.
Spliced
MRNA
27
What is transcription?
Making mRNA to DNA
28
What is mRNA and what does it do?
Messenger RNA
A long single strand created during transcription in which the base sequence is complementary to DNA
29
What is codon?
mRNA strand being read in triplets
30
What is anticodon?
Triplets that read on tRNA
31
Where does transcription take place?
In the nucleus
32
Where does translation take place?
Cytoplasm
33
Describe the process of transcription.
1. The hydrogen bonds in the DNA, between complementary base pairs, is broken by an enzyme.
• two exposed strands, one used as a template.
2. One of the DNA strands is used as a template to make the mRNA molecule, the template is called the antisense strand.
3. Free nucleotides line up by complementary base pairing and adjacent nucleotides are joined by phosphodiester bonds thus forming a molecule of mRNA.
• The enzyme RNA polymerase catalyses the formation of phosphodiester bonds.
4. When a stop codon is reached this ceases. As the RNA polymerase moves away the DNA rejoins, with only 12 bases being exposed at a time to reduce the chance of damage to the DNA.
5. In eukaryotic cells the pre-mRNA is then spliced to remove the introns leaving just a strand of exons.
6. The mRNA then moves out of the nucleus through a pore and attaches to a ribosome in the cytoplasm which is the site of next stage of protein synthesis called translation.
34
Transcription
1. The ____________bonds in the DNA, between complementary base pairs, is broken by an enzyme.
• two exposed strands, one used as a template.
2. One of the DNA strands is used as a template to make the mRNA molecule, the template is called the _________ strand.
3. Free nucleotides line up by complementary base pairing and adjacent nucleotides are joined by _________________ bonds thus forming a molecule of mRNA.
• The enzyme RNA ___________ catalyses the formation of phosphodiester bonds.
4. When a ______ codon is reached this ceases. As the RNA polymerase moves away the DNA rejoins, with only 12 bases being exposed at a time to reduce the chance of damage to the DNA.
5. In___________ cells the pre-mRNA is then spliced to remove the introns leaving just a strand of________.
6. The mRNA then moves out of the nucleus through a ______ and attaches to a ribosome in the cytoplasm which is the site of next stage of protein synthesis called translation.
Hydrogen
Antisense
Phosphodiethster
Polymerase
Stop
Eukaryotic
Exons
Pore
35
Describe the process of translation.
1. mRNA attaches to a ribosome
2. transfer RNA collects amino acids from the cytoplasm and carries them to the ribosome.
• can only carry one type of amino acid, and a triplet of bases (anticodon) at the other.
3. tRNA attaches itself to mRNA by complementary base pairing
• two molecules attach to mRNA at a time.
4. The amino acids attached to two tRNA molecules join by a peptide bond and then tRNA molecules detach themselves from the amino acids, leaving them behind.
5. This process is repeated thus leading to the formation of a polypeptide chain until a stop codon is reached on mRNA
• this ends the process of protein synthesis.
36
Translation
1. mRNA attaches to a_________.
2. transfer RNA collects amino acids from the ___________ and carries them to the ribosome.
• can only carry ___type of amino acid, and a triplet of bases (anticodon) at the other.
3. tRNA attaches itself to mRNA by___________ base pairing
• ___ molecules attach to mRNA at a time.
4. The amino acids attached to two tRNA molecules join by a _________ bond and then tRNA molecules detach themselves from the amino acids, leaving them behind.
5. This process is repeated thus leading to the formation of a polypeptide chain until a _____ codon is reached on mRNA
• this ends the process of protein synthesis.
Ribosome
Cytoplasm
One
Complementary
Two
Peptide
Stop
37
Where does meiosis take place?
Sex organs
38
What does meiosis produce?
4 genetically different gametes
39
_________ cells contain chromosomes in pairs.
Diploid
40
What are homologous chromosomes?
Chromosomes that have exactly the same genes
41
Describe the process of crossing over of chromosomes.
Two chromosomes in a homologous pair come together. The chromatids of the two chromosomes wrap around each other to form a bivalent. Parts of the chromatids can break off and exchange between homologous chromosomes. These are recombinant chromosomes. Because the chromosomes have exchanged DNA that means they can exchange alleles.
42
What is the chiasmata in crossing over?
Where crossing over chromosomes are joined.
43
What does crossing over of chromosomes form?
A bivalent
44
What are recombinant chromosomes?
Chromosomes in which the maternal and paternal chromosomes have changed DNA by crossing over
45
What are the names of the stages of meiosis?
Interphase
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Cytokinesis
Prophase 2
Anaphase 2
Metaphase 2
Telophase 2
Cytokinesis
46
Describe the process of interphase.
The cell copies the chromosomes and organelles.
The chromosomes are not visible as distinct structures during interphase.
47
Describe the process of prophase.
- chromosomes condense and become visible.
- homologous chromosomes link together forming chiasmata. When the chromosomes are paired like this we called it a bivalent. At this point crossing over can take place, exchanging alleles between homologous chromosomes.
- the nuclear membrane breaks down.
- the centrioles move to opposite poles of the cell.
- spindle fibres also start to assemble into the spindle apparatus.
48
Describe the process of metaphase.
The pairs of homologous chromosomes are lines up on the equator of the spindle apparatus.
49
Describe the process of anaphase.
- the spindle fibres shorten and the homologous chromosomes move towards opposite poles.
- for this to happen the chiasmata between the homologous chromosomes break.
50
Describe the process of telophase.
- the chromosomes have now reached the poles of the cell.
- at this point the nuclear membranes reform and the chromosomes uncoil back to their chromatin state.
51
Describe the process of cytokinesis.
- the cell divides into two haploid cells - they no longer contain pairs of homologous chromosomes.
52
What does meiosis produce?
4 haploid gametes
53
What is independent assortment?
In metaphase 1 , when homologous chromosomes pairs line up on the spindle we can’t predict wether the paternal or maternal chromosome will end up in each gamete.
54
How do you calculate the number of genetically different gametes produced by independent assortment?
2n (to the power of n) n= number of homologous chromosome pairs.
55
What are the two ways in which meiosis produces genetic variation in its gametes?
Crossing over
Independent assortment
56
What are the features of the genetic code?
• non-overlapping: meaning that each triplet is only read once and triplets don’t share any bases.
• Genes are separated by non-coding repeats of bases.
• is degenerate: meaning that more than one triplet codes for the same amino acid,
--> this reduces the number of mutations which are mistakes in the base sequence such as base deletion, insertion or substitution.
57
Gene mutations involve a change in the ______ ________ of chromosomes.
Base sequence
58
Due to the ___________ nature of the genetic code, not all base substitutions can cause a change in the sequence of encoded amino acids.
Degenerate
59
_________ __________ can increase the rate of gene mutation.
Mutagenic agents
60
What are the 3 types of mutation?
Substitution mutation
Deletion mutation
Non - disjunction
61
What is substitution mutation?
Where one base is substituted for another
62
what is deletion mutation?
Where one base is deleted
63
What is non-disjunction mutation?
Mutation in the number of chromosomes
64
What is a frame shift mutation?
Where a deletion of a base leads to the bases shifting
65
What are the advantages of asexual reproduction?
- identical clones - can survive in a stable environment
- only 1 parent needed - quicker as do not have to look for a mate/pollinator, no courtship
66
what are the advantages of sexual reproduction?
- genetic variation - offspring more adapted to environment
67
What is a disadvantage of asexual reproduction?
- less resilient to disease
- vulnerable to changes in condition
- competition for resources
68
What are the disadvantages of sexual reproduction?
- have to raise young (not in all cases)
- courtship
- look for mate
69
Tick:
Feature of division: Mitosis Meiosis
One cell division I
Two cell divisions I
DNA replicates I
Formation of bivalent and chiasmata I
Crossing-over I
Independent segregation of homologous chromosomes. I
Separation of chromatids I
Two daughter cells end products I
Four daughter cells end products I
Daughter cells are haploid I
Daughter cells are diploid (if original cell was diploid) I
New combinations of alleles produced in daughter cells I
1. Mitosis
2. Meiosis
3. Mitosis + meiosis
4. Meiosis
5. Meiosis
6. Meiosis
7. Mitosis + meiosis
8. Mitosis
9. Meiosis
10. Meiosis
11. Mitosis
12. Meiosis
70
What type of selection is antibiotic resistance an example of?
Directional selection
71
What is human birth weight an example of?
Stabilising selection
72
Interspecific variation
Variation between different species
73
Intraspecific variation
Variation within members of the same species
74
What is sampling?
Taking measurements of selected individuals from the population being investigated
75
Why might sampling measurements not be representative?
Sampling bias - selection process may be biased, unrepresentative choices, deliberately or unknowingly
Chance- pure chance
76
How do you conduct a random sample?
- divide study area into a grid of numbers and lines
- using random numbers from a table or computer generator, obtain a series of coordinates
- take samples at the intersection of each pair of coordinates
77
How can you minimise the effect of bias?
- use a large sample - more reliable data
- analysis of data collected - determine the extent to which chance may have influenced the data
78
What are the characteristics of a normal distribution curve?
- mean median and mode are the same
- curve never touches the x axis
- shows continuous variation
79
What is standard deviation a measure of?
The spread of data about the mean
80
+ SD =?
_
68% spread about the mean
81
+ 2SD =?
-
95% spread about the mean
82
What does P=0.05 mean?
The probability of the value being due to chance is more than 5%
83
Define a population.
A group of organisms in the same place at the same time that are able to interbreed and produce fertile offspring
84
What are the 3 types of adaptation?
Behavioural
Physiological
Anatomical
85
Behavioural adaptation
The way an organism acts to increase its chance of survival e.g. hibernation
86
Physiological adaptation
An internal process that can regulate homeostasis/benefit it in its environment eg snake venom
87
Anatomical adaptation
Structural feature/ becomes fitted to its environment e.g. polar bears have white fur
88
In order for natural selection to occur there needs to be _______________ within a population.
Variation
89
Describe the process of natural selection
- new alleles are brought about by mutations
- the new allele is advantageous and therefore organisms are more likely to survive and reproduce
- pass on advantageous allele to offspring
- frequency of allele will increase
90
Natural selection
- new alleles are brought about by _________
- the new allele is advantageous and therefore organisms are more likely to survive and reproduce
- pass on advantageous allele to __________
- frequency of allele will increase
Mutations
Offspring
91
Genetic drift
A change in a population’s allele frequencies that occurs due to change rather than selective pressures. E.g an ice age
92
Directional selection
Occurs when environmental conditions change. Individuals with phenotypes suites to the new conditions will survive and pass on their genes. Over time the mean of the population will move towards these characteristics
93
Founder effect/ genetic bottleneck
an extreme example of genetic drift that happens when the size of a population is severely reduced. Events like natural disasters (earthquakes, floods, fires) can decimate a population, killing most individuals and leaving behind a small, random assortment of survivors.
94
Directional selection
For one extremes trait.
Against the other extreme trait
Normal distribution curve, bell curve shifts
95
Stabilising selection
For moderate traits
Against both extremes
Selection for mean values
Extremes are selected against
96
Disruptive selection
For both extremes
Against moderate traits
Diverse into 2 populations
Mean is not favoured
97
Describe how antibiotic resistance is an example of directional selection
- variation - some strains of bacteria and some aren’t
- competition - non-resistant bacteria are killed (e.g by penicillin)
- survival of the fittest - resistant bacteria survive
- passing on of genes - the resistant bacteria reproduce and pass on their adaptations to their offspring
98
Explain how human birth weight is an example of stabilising selection
- variation - there are a variety of weights a baby can be born
- competition - a normal weight is beneficial. Too small/large can make it hard to survive
- natural selection - keeps weights in the middle range. Mean weight survive and pass on adaptations to offspring
99
What did Carl Linnaeus group organisms by?
Structure and characteristics
100
Who created the binomial name system?
Carl Linnaeus
101
Describe the binomial name system
The genus goes first with a capital letter, followed by the species with a lower case
Written in italics
102
define a species
A group of organisms who share similar genes, and can reproduce to produce fertile offspring
103
What is phylogeny?
The evolutionary relationship between organisms
104
What are the elements of phylogenic classification?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
105
Name a domain (on spec)
Eukarya
106
Name the kingdoms (on spec)
Animal, fungi, plant, bacteria, protoctista
107
Name a phylum (on spec)
Chortada
108
Name a class (on spec)
Mammals
109
What does a phylogenic tree show?
How closely organisms are related
Common ancestors
110
What system did Carl Woese create?
3 domain system
111
Which classification system is currently used?
3 domain - Carl Woese
112
How did Carl Woese create the 3 domain system?
Used evidence from chemical analysis
113
What makes up the 3 domain system?
Archaea
True bacteria
Eukaryotes
114
Courtship behaviour is carried out by organisms to attract a mate of the right_______.
Species
115
Courtship behaviour is ___________ specific
Species
116
why is courtship behaviour species specific?
prevents interbreeding, making reproduction more successful (as mating with the wrong species won't produce fertile offspring).
117
The more closely related species are, the more _______ their courtship behaviour.
Similar
118
Courtship behaviour can be a way to signal ____________ maturity
Reproductive
119
Courtship behaviour is a way to form a ______ with their pair, to increase reproductive success - not necessary for all species
Bond
120
Courtship behaviour can be used for ______________ mating with other individuals in some species
Synchronised
121
What is biodiversity?
This is the general term used to describe the variety in the living world.
122
How can you measure species diversity?
Simpson’s diversity index
123
Biodiversity reflects how well an __________ functions.
Ecosystem
124
How does diversity index relate to the stability of an ecosystem?
• The higher the species diversity index, the more stable the ecosystem usually is.
125
An ecosystem with a high diversity index is more likely to have at least one _______ which may survive a change in conditions e.g. A drought
Species
126
Species diversity
refers to the number of different species and the number of individual species within a community.
127
Genetic diversity
refers to the variety of genes possessed by the individuals that make up any ONE species.
128
Ecosystem diversity
refers to the range of different habitats within a particular area
129
A community dominated by one or two species is considered to be _____ diverse than one in which several different species have a similar abundance. Simpson's Diversity Index is a measure of diversity which takes into account the number of species present, as well as the relative abundance of each species. As species richness and evenness_______, so diversity increases.
Less
Increase
130
In extreme conditions, the communities in an ecosystem are dominated by the ________ rather than the species within them.
Climate
131
What is the diversity index in extreme environments?
Low
132
What is the diversity index in less hostile environments?
High
133
Name some natural threats to biodiversity.
Low population
Low breeding rate
Natural disasters
134
Name some human threats to biodiversity.
Habitat modification
Overexploitation of selected species
Global warming
Hunting
Pollution
135
What is the impact of agriculture on species diversity ?
Decreases species diversity
136
Why does agriculture decrease species diversity?
Farmers select one species which reduces the genetic variety by reducing the alleles to the ones they desire
Competition and the addition of pesticides adds up to a loss of species diversity
137
What is the effect of hedgerows on species diversity? Why?
They increase the species diversity
They house rare and fragile species e.g wild flowers, insects, birds and small mammals
138
What are the 4 methods of investigating genetic diversity?
- genome sequencing
- mRNA sequencing
- amino acid sequencing
- immunological comparisons
139
Why can’t you classify organisms on their appearance alone?
- the same characteristics could be coded for by more than one gene
- the same characteristics could haves arisen separately
- the characteristics could have been influenced by the environment and not the genes
140
What is interspecific variation?
The difference between species
141
What is intraspecific variation?
Variation within one species
142
What is genome sequencing?
• uses gene technology to read the base sequences of organisms. The genetic diversity of a species can be measured by sampling DNA.
• More closely related individuals should have less variation in the DNA base sequences.
143
What is mRNA sequencing?
• Traits are due to genes being expressed, through expression mRNA is used.
• So by looking at mRNA we can see what genes are expressed and what they code for.
More closely related organisms should have more similar mRNA sequence.
- mRNA sequencing only shows the expressed genes in a genome
144
What is amino acid sequencing?
• The sequence of amino acids can be studied as this can be taken back to the mRNA sequence and thus the DNA sequence.
• Related organisms have similar DNA sequences , hence similar amino acid sequences, hence similar proteins.
145
What are immunological comparisons?
• Similar proteins will bind to similar antibodies
○ Example: human antibody might bind to same antigen as chimpanzee antibody, but not as rabbit antibody as they are more distantly relatives.
• Fewer the number of similar antigens the less precipitate is formed and the more distantly the species are related.
146
Describe the process of an immunological comparison.
- serum allium from species A (human) is injected into species B (rabbit).
- species B (rabbit) produces antibodies specific to all the antigen sites on the Adium from species A (human).
- serum is extracted from species B (rabbit); this serum contains antibodies specific to the antigens on the allium from species A.
- serum from species B is mixed with the blood from a third species (species C)
- the response is the formation of a precipitate. The greater the number of similar antigens, the more precipitate is formed and the more closely the species are related.
