Module 5: Heredity Flashcards
1
Q
What is sexual reproduction?
A
the process of forming a new organism from the fusion of the offspring’s parents male and female gametes. They are not geneticall identical.
2
Q
What does sexual reproduction require?
-what happens
A
Requires (meiosis) for the production of gametes- to form a zygote with a full complement of chromosomes. Each gamete is haploid. The cells of the zygote divide (mitosis) and the embryo continue to grow.
3
Q
What is asexual reproduction?
A
The process of forming an offspring from just one parent through cell division. There is no fusion of gametes. They are genetically identical.
4
Q
What is reproductive success?
A
The ability to reproduce of an individual
5
Q
What is the gene pool?
A
The genetic material of all organisms in a population
6
Q
What is the biological fitness?
A
The likelihood of genes appearing in the next generation
Important for continuation of a species
7
Q
What is internal fertilisation?
A
The fusion of gametes inside of the body of a parent
8
Q
What animals use internal fertilisation?
A
Terrestrial animal typically use this to prevent exposure and desiccation of gametes or embryos
9
Q
what are the benefits of internal fertilisation?
A
Offers more protection to gametes and embryos but puts parent at survival risk
More selective of their mate
Less chance of desiccation
10
Q
What is external fertilisation?
A
The fusion of gametes outside of the body of a parent
11
Q
What animals use external fertilisation?
A
Aquatic animal use the water as a medium for the gametes to travel
12
Q
What are the pros and cons for external fertilisation?
A
It is susceptible to environmental influences e.g. predators and PH changes
Use of spawning to release large quantities of gametes to compensate for losses ( requires a short burst of high energy)
Easier way to find mates
More genetic variation
13
Q
Do flowers reproduce asexually or sexually?
A
both
14
Q
ROLE OF
Flowers
petal
nectar
A
flowers are the reproductive organs of sexually producing plants; the petals and nectar are used to lure animals and to assist with delivery of pollen.
15
Q
Sexual reproduction in plants
A
Offspring are produced by the fusion of two haploid gametes. Male gametes (pollen) are produced and transferred to the female ovules. Pollination is assisted by wind or insects. After pollination, fertilisation ( after pollen lands on stigma, a pollen tube grows down through the style into the ovary. It is then moved down to try to fertilise the ovules) occurs and the ovules grow into seeds in a fruit, which disperses once ripe. The seed is then freed from the fruit.
16
Q
Plants pollination sexual
A
Male gametes (pollen) are produced and transferred to the female ovules. Pollination is assisted by wind or insects. after pollen lands on stigma, a pollen tube grows down through the style into the ovary. It is then moved down to try to fertilise the ovules
17
Q
Where do seeds grow in plants?
A
the ovules grow into seeds in a fruit, which disperses once ripe. The seed is then freed from the fruit.
18
Q
What are the male parts of a plant?
A
Stamens are made up of:
The filament- supports the anther
Anther- pollen produced here
19
Q
What are the female parts of a plant?
A
Carpel is made up of the
Stigma: pollen grains reach the stigma (pollination)
Style: pollen tube grows down through the style into the ovary
Ovary: where eggs cells are
20
Q
Advantages and disadvantages of sexual reproduction in plants?
A
Advantages: Creates a genetic diversity within a species, leading to higher levels of disease resistance and a greater ability to adapt to changing conditions.
Disadvantages: Can prevent favourable genes from being passed to offspring
21
Q
What is asexual reproduction in plants?
A
Structural modifications to the stem or roots of the plant results in the production of new individuals, without the need for production of seeds or spores
22
Q
What is vegetative propagation? Provide examples
A
It results in the parent producing a plant that is genetically identical. E.g. cuttings, runners and bulbs
23
Q
Cuttings in plants:
A
Cuttings: the stem from the plant is cut and planted into soil, eventually grows into another plant
24
Q
What is totipotency?
A
Totipotency- each cell has the ability to do the job of every other cell
25
Runners in plants:
Runners: Stems extending from the plant along the soil, nodes develop along it which extend into the soil and form a new plant root. Here another plant can grow while being connected to the parent plant
26
Bulbs in plants:
Bulbs: Underground food storage organs. When a new plant forms the bulb provides nutrients for the plants survival
27
advantages of asexual reproduction in plants
Advantages: Offsprings are clones of parent plants, meaning the favourable traits are effectively passed through generations. This is economically advantageous for farmers to ensure consistency in their crops. It is less energy-intensive, meaning the population can increase rapidly and exploit suitable habitats quickly
28
Disadvantages of asexual reproduction in plants
Disadvantages: Pathogens may spread easily from parent to offspring, resulting in less genetic diversity. This increases the susceptibility of species to new diseases, and evolution is reduced due to lack of genetic variation.
29
How do funghi sexually reproduce?
Plasmogamy: two genetically different cells fuse together
Karyogamy: the nuclei fuse
Meiosis: gametes are generated which produce spores that are distributed into the environment
30
Fungi asexual reproduction: fragmentation
Fragmentation: pieces of hyphae can separate and become new colonies
31
List the ways in which fungi can asexually produce
fragmentation, budding and spores
32
Fungi asexual reproduction: Budding
the nucleus divides and a bulge forms in the side of the cell which is then split off by cytokinesis, and the bud detached itself from the mother cell when it is of a sufficient size. This separated cell can support itself independently and undergoes further cell division to produce more bud cells.
33
Fungi asexual reproduction: SPores
mitosis or mitosis produces genetically identical cells to the parent, which are distributed into the environment by wind or vectors . Spores differ from gametes as they do not need to combine with another spore to form offspring. Hyphae (fine thread like structures) branch out and have ends that are capable of producing sporangia.
Sexual spores may be developed when opposite gender hyphae combine to develop a zygospore, The zygospore is diploid and each hypha are haploid. The zygospore undergoes meiosis to produce haploid spores which are dispersed into the environment. The process repeats and results in genetically different hyphae.
34
Advantages and disadvantages reproduction in fungi
advantages:
Production of spores allows for offspring to be widely distributed, increasing colonisation
They can be produced in large numbers
Combination of sexual and asexual methods means fungi have a choice
Asexual is fast and not energy-intensive
Sexual increases genetic variability
Disadvantages:
Asexual reproduction may result in offspring which are only suited to one habitat
35
How do bacteria reproduce?
Binary fission
36
Binary fission in bacteria:
A single cell divides into two identical daughter cells
Begins with DNA replication where it is copied and divided into two
The cell elongates and splits in two (cytokinesis), producing daughter cell clones
37
Binary fission in bacteria: advantages
Very rapid and only requires a single organism in order to produce offspring
38
Binary fission in bacteria: disadvantages
Lack of genetic diversity, lower chance of organism survival. Thus can be overcome by high rates of mutation during DNA replication and HGT which can be passed from bacteria to bacteria
39
Sexual reproduction in protists
For haploid protists, two haploid cells fuse to form a zygote. Genetic material is combined in a new, fused nucleus. The zygote undergoes meiosis to form new haploid cells
For diploid protists, adult cells undergo meiosis to produce 4 gametes. Gametes fuse during fertilisation to form a diploid zygote.
40
Asexual reproduction in protists
Binary fission is the most predominant method
| Budding occurs when a new organism grows from the body of the parent organism to form a new colony
41
Protists reproduction: Advantages + Disadvantages
Advantages:
If they reproduce sexually they have an evolutionary advantage over asexually producing protists.
Allows for greater variation
Disadvantages:
Asexual reproduction can often be disadvantageous to host organisms during pathogenesis. Fast reproduction at little energy cost to the protist makes them more effective as disease-causing agents
42
Define fertilisation:
Fertilisation: Gametes meeting and combining to form a zygote
43
What is Gametogenesis?
Gametogenesis is the name of the gamete formation process and can be divided into spermatogenesis (producing sperm) and oogenesis (formation of mature egg cells).
44
What is spermatogenesis?
producing sperm
45
What is oogenesis?
formation of mature egg cells
46
What hormone is produced in the testes?
| -what is its role
The hormone testosterone is produced in the testes and plays a role in producing sperm cells.
47
Fertilisation in humans:
The fertilisation occurs in one of the fallopian tubes of the female's body. The sperm enters the vagina, travels up through the uterus and then along one of the fallopian tubes where it can combine and fertilise the mature egg.
48
How does a zygote form? Humans
The gametes fuse to form a zygote, a single cell with 46 chromosomes (23 from each parent).
49
How does a blastocyst form?
During fusion, the head of the sperm cell detaches from its tail (flagellum) and activates the egg resulting in cell division. The resulting product is called a blastocyst.
50
What is implantation? humans
The process whereby the blastocyst adheres to the walls of the uterus.
51
Why is implantation important?
This establishes the blastocysts access to nutrients, allowing it to develop into an embryo ( blood vessels surrounding the blastocyst carry blood which has dissolved nutrients).
52
What happens if the blastocyst implants successfully in the uterus?
If the blastocyst implants successfully in the uterus, the cells continue dividing, moving to form two distinct structures.
53
Implantation:
| -inner cell mass
Three or four blastocyst cells develop into the inner cell mass, which over the next few weeks will form into the recognisable structures of a human embryo, with a head, beating heart and tiny limbs. Some of these cells also develop into a foetal membranes that form a fluid-filled protective ‘bag’ around the embryo.
54
Implantation
| -trophoblast
The remaining 100 or so blastocyst cells form a structure called the trophoblast, which will provide the baby’s contribution to the placenta.
55
How is HCG produced?
It is produced by the placenta after implantation.
56
WHy is HCG important?
It is mainly responsible for the early pregnancy symptoms ranging from missed menstruation to nausea, vomiting and fatigue.. It supports the function of the corpus luteum, a temporary structure in the ovaries essential in early pregnancy. It's the hormone detected by pregnancy results.
57
Outline HCG trends throughout pregnancy:
Increases drastically in the first 10 weeks and slowly declines throughout the pregnancy
58
What does progesterone do?
It maintains the functionality of placenta and prevents sudden movement and contraction of the uterus. It stimulates growth of blood vessels that supply the womb and inhibits contraction of the uterus so it grows as the baby does. It also strengthens pelvic wall muscles for labour.
59
Outline progesterone trends throughout pregnancy:
Progesterone levels rise after the first trimester
60
What is oesterogen?
It is an ovarian hormone that is controlled by luteinising hormone (LH) that triggers ovulation.
61
What is oestrogens role during pregnancy?
An important role of estrogen is to facilitate the maturing of lungs, kidneys, adrenal gland, liver and bone It helps the uterus grow, maintains its lining, activates and regulates production of other hormones.
62
Outline oestrogen trends throughout pregnancy;
oestrogen levels increase steadily during pregnancy and reach their peak in the third trimester. The rapid increase in estrogen levels during the first trimester may cause some of the nausea associated with pregnancy.
63
What is the role of oxytocin?
Facilitates the delivery process by helping in the control of the uterus and also stimulates the mammary glands to produce milk.The hypothalamus in the brain produces oxytocin and stores it in the pituitary gland (situated below the hypothalamus). Upon stimulation of hypothalamus neuron cells, the pituitary gland will secrete oxytocin into the blood.
64
Oxytocin levels at labour + effect
Oxytocin levels rise at the start of labour stimulating contractions of uterine muscles. It triggers production of prostaglandins, which increase contractions further.
65
Outline oxytocin trends throughout pregnancy:
increased from the first to the third trimester of pregnancy, with a huge increase towards the end of the pregnancy to help with labour
66
How has scientific knowledge had advancements?
| -intro statement
The increase in and proliferation of scientific knowledge has led to huge advancements in agriculture, enabling processes to become more efficient and productive. We have been able to manipulate the fundamental principles of reproduction to produce desired outcomes.
67
Selective breeding scientific advancements:
Based on the understanding that phenotypic traits are hereditary, so farmers selectively mate plants with desirable traits
This can influence cross-breeding or pure-breeding practices
E.g. Jersey or Angus Cows
68
Artificial insemination scientific advancements:
Benefits: timing (able to synchronize births), passing of favourable traits and ensuring successful pregnancy increases yields
Method:
Detection of female cows in oestrus
Collection of semen can be done manually or through stimulation
Insemination usually performed using an insemination gun which shoots semen into the cervix of the desired animal
69
artificial pollination scientific advancements:
Benefits: cross-breeding of favourable traits, self-pollination and ensuring successful pollination of all plants, resulting in high crop yields
Method:
Pollen removed from the stamen of one plant
Pollen applied to the stigma of another plant
The pollen fertilises the ovum
70
Genetic engineering scientific advancements:
```
Knowledge of DNA structure and improvement of genetic techniques (e.g. gene cloning) has allowed agriculturalists to manipulate organisms on a fundamental level. This has allowed the introduction of new desired traits into organisms such as:
Bt cotton (insect resistance)
Golden rice (increased nutritional value)
Strawberries (frost-resistance)
It is estimated that more than 170million hectares of GM crops were grown globally in 2012
```
71
What is the cell cycle?
Most cells grow, perform the activities needed to survive and divide to create new cells. This is replicated throughout the life of a cell.
72
what is the most important stage of the cell cycle?
The division portion of the cell cycle is extremely important as this is the point when genetic information is passed to its offspring cells
73
What does division in the cell cycle ensure?
The division ensures that new cells are able to replace the older cells within an organism whenever those cells die
74
What is mitosis?
When the cell nucleus divides into two
| One cell replicates in genetic nucleus content exactly and then divides to become two cells
75
How does mutation occur?
if cells divide in an uncontrolled manner, tumour or cancer may result
76
why is cell division essential?
Cell division is essential for the continued growth of organisms and for the repair of damaged/ worn-out cells within them
77
Mitosis explained (detailed)
Interphase: DNA has replicated but has not formed the condensed structure of the chromosome. The nuclear membrane is still intact to protect the DNA molecule from undergoing mutation.
Prophase: The DNA molecules progressively shorten and condense by coiling, to form chromosomes. The nuclear membrane is no longer visible. The spindle apparatus has migrated to opposite poles of the cell.
Metaphase: (middle)The spindle fibres attach themselves to the centromeres of the chromosomes and align at the chromosomes at the equatorial plate.
Anaphase: (away) The spindle fibres shorten and the centromere splits, separated sister chromatids are pulled along behind the centromeres.
Telophase: (two) The chromosomes reach the poles of their respective spindles. Nuclear envelope reform before the chromosomes uncoil. The spindle fibres disintegrate.
Cytokinesis: The splitting of the daughter cells. A furrow forms and the cell is pinched in two. Each daughter cell contains the same number and quality of chromosomes.( In plant cells: cytokinesis involves a cell plate while the nucleus is still in telophase).
78
Mitosis explained (simple)
Interphase- DNA replicated
Prophase- condense and form chromosomes, at opposite poles of the cell
Metaphase- sister chromatids are pulled along behind the centromere
Telophase- Chromosomes reach poles, daughter cells
Cytokinesis- the splitting of the daughter cells
79
What is meiosis?
A form of cell division happening in sexually reproducing organisms by which two consecutive nuclear divisions occur leading to the production of four haploid cells, with the maternal and paternal chromosomes being distributed randomly between the cells.
80
Meiosis and genetic variation:
Genetic variation arises as a result of the behaviour of chromosomes: during the crossover and when chromosomes randomly segregate and paternal and maternal chromosomes assort independently of each other (2 to the power of 23)
81
Meiosis 1
Chromosomes line up in homologous pairs ( one maternal and one paternal) during prophase 1
Crossing over occurs: arms of homologous chromosomes exchange material during metaphase.
Crossing over ensures that linked genes on chromosomes can be inherited independently of each other.
The exchange of genetic material causes the mixing of paternal and maternal genes and results in an increased combination of genes that may be transmitted by gametes to offspring
The chromosomes in each pair of chromosomes separate during anaphase 1, so that entire chromosomes of each pair move into a daughter cell.
The separation (random segregation) ensures the gametes will be half that of the original cell
Independent assortment occurs
82
Meiosis 2
The two daughter cells that result from Meiosis 1 undergo meiosis 2, but it does not further affect genetic variation
83
Stages of meiosis:
Early prophase: chromosomes separate out into homologous pairs
Late prophase: Nuclear membrane breaks down, chromosomes split into chromatids and crossing over occurs
Metaphase 1: chromosomes align in pairs in the middle, random segregation
Telophase: Two daughter cells form, chromosome number halved
Cytokinesis 1: Daughter cells are not identical and have half the original number of chromosomes
Metaphase 2: Chromosomes align at the equator
Anaphase 2: Chromatid move apart to opposite poles
Cytokinesis 2: Four resulting daughter cells are not identical to each other and have half the original chromosome number
84
What is DNA?
the genetic material that organisms inherit from their parents.
85
What is a gene?
a discrete unit of hereditary information consisting of a specific section of DNA.
Short lengths of DNA make up genes so genes have the same chemical composition as DNA.
86
What is a DNA molecule?
A DNA molecule is very long and usually consists of hundreds of thousands of genes.
87
DNA replication basic
When a cell reproduces itself by dividing, its DNA is copied and passed along from one generation of cells to the next.
Encoded in the structure of the DNA is information that programs all the cell’s actions
88
What is a chromosome?
Compact coils of thread-like molecules called DNA, organised around proteins called histones
Chromosomes consist of 40% DNA and 60% proteins (histone).
89
genes in chromosomes:
Chemically, each gene is made up of a portion of DNA that stores information as a coded sequence, and each coding sequence/gene is located at a particular site or locus on the chromosome
90
What doe the coded info in genes determine?
The coded information within genes determines how living things look, behave and function or phenotypes.
91
What are homologous pairs of chromosomes?
Maternal and paternal chromosomes that carry alleles of the same genes are known as homologous pairs of chromosomes
92
What happens to the chromatin when cells begin to divide?
When cells begin to divide, the chromatin material coils into short, thick, rod-shaped chromosomes for easy transfer
93
What did Watson and crick's model reveal?
They revealed that DNA is a double helix or ‘twisted ladder”
94
What are nucleotides?
A DNA molecule is made up of two chains/strands of monomers called nucleotides
95
What does each nucleotide consist of?
Each nucleotide consists of a phosphate, deoxyribose sugar and a nitrogenous base
96
What are the bases?
Adenine (A), Thymine (T), Guanine (G) and Cytosine (C)
97
How are the bases arranged?
The bases are arranged in a sequence along each strand of DNA, each DNA molecule is thousands of bases long
The whole molecule spirals and is therefore known as the double helix
There is a leading strand and a lagging strand
98
Chemical structure of DNA:
Each of the two complementary strands in a DNA molecule is made up of a sequence of many nucleotides. The strands are held together by weak hydrogen bond in the centre
The vertical side of the ladder are made up of a sugar-phosphate backbone and the rungs of the ladder are pairs of nitrogenous bases
The 4 bases pair A-T and G-C
99
What is DNA replication?
The replication of the long sequences accounts for the replication of the genetic code of an organism
During meiosis and mitosis, it is necessary for the DNA to make an exact replication of itself
100
How does DNA replication occur?
The DNA double helix is unwound by the enzyme helicase
The DNA unzips forming two single strands
Nucleotides are attached to the single strands resulting in two identical strands of DNA by DNA polymerase (enzyme). The two double-stranded molecules are chromatids.
101
What do the enzymes do in DNA replication?
Primase sends a signal for the starting point for DNA polymerase
Ligase glues together small sections of DNA
This process passes on the genetic information from generation to generation
102
Sexual reproduction DNA replication:
| + fertilisation
During sexual reproduction, the genetic code is copied and then half of the genetic information passes into each of the daughter cells
When fertilisation occurs the new organism has half the genetic material from each parent
103
anther
produces pollen
104
filament
long thin stalk attached too flower
105
stigma
head of the pistil- stickiness helps catch pollen
106
style
long thin stalk- pollen creates a tube through this to reach ovules for fertilisation
107
sepal
leaf-like structures at the base of the flower
108
ovule
egg cells of the plant
109
ovary
at the base of the pistil- contains the ovules and eventually forms the fruit
110
Why does meiosis occur twice?
Cells undergoing mitosis just divide once because they are forming two new genetically identical cells whereas in meiosis cells require two sets of divisions because they need to make the cell a haploid cell which only has half of the total number of chromosomes.
111
What is the fundamental heredity unit? why?
DNA as it directs all processes in a cell
Reproduction is dependent upon DNA replication
Replication ensures that important information is transferred down the generations
112
Why is DNA replication important?
- Reproduction of cells is dependent upon DNA replication, as the creation of new cells requires more DNA to be produced
- By copying the genetic material of a cell, replication ensures that information important for life is transferred down through the generations
- If DNA were not replicated before mitosis and meiosis, cell division would have the amount of DNA, and resulting cells would die due to inadequate amounts of genetic information
- DNA replication is a high-fidelity process, ensuring that daughter DNA strands carry the same gene, and encoding all the essential proteins for life.
113
why is mitosis essential?
Mitosis is essential for development and growth of organisms. Mitosis increases the number of cells in an organism, allowing for development of multicellular bodies.
Mitosis also allows for old cells to be replaced, ensuring that tissues continue to function effectively and efficiently.
114
what is mitosis' importance in reproduction?
For organisms like humans, mitosis allows us to develop maturity when we. And pass our genetic information onto offspring through sexual reproduction.
- Some organisms reproduce by asexual reproduction, which is facilitated by mitosis. In these cases, mitosis creates the next generation of molecules
115
What is the end product of meiosis?
gametes
116
How does meiosis increase variation? why is this important?
meiosis purposefully introduces variation. Processes of crossing over, independent assortment and random segregation allow for combinations of different alleles, increasing variation in offspring and the wider population.
Genetic diversity (introduced by meiosis and sexual reproduction) is very important for the continuity of species, as mutation and variation are essential factors for survival and evolution.
117
Does mitosis or meiosis purposely increase variation?
meiosis
118
how does DNA exist in a eukaryotic cell?
Eukaryotic DNA is found wound tightly around histones, helping the DNA condense. These form supercoils, which are then packed together to form chromosomes. On average, eukaryotes have larger genomes than prokaryotes, with long non-coding and repetitive sequences. Eukaryotes DNA is linear.
119
what are histones?
A histone is a protein that provides structural support to a chromosome
120
how does DNA exist in a prokaryotic cell?
Prokaryotic cells have free-floating, circular chromosomes found in the cytoplasm
The DNA is not bound or packaged by proteins unlike in eukaryotes
Prokaryotes have smaller, more compact genomes, with very little repetitive DNA. They also have small, extra-chromosomal segments called plasmids
Plasmids are able to be transferred between organisms to pass genetic material horizontally within generations
121
what is nRNA?
The intermediary molecule called mRNA transmits information out of the nucleus for processing. mRNA is a messenger ribonucleic acid. It is chemically quite similar to DNA, except that it is a single-stranded, contains a ribose sugar instead of a deoxyribose sugar, and instead of thymine (T) nitrogenous base, it has uracil (U) in its place.
122
steps involved in transcription:
1. RNA polymerase binds to the promoter sequence upstream up from a gene.
2. As RNA polymerase moves along the DNA strand, a small region of DNA is unwound
3. RNA polymerase ‘reads’ the DNA template strand, matching complementary free-floating nucleotides (NTPs) to create a chain containing the same coding information.
4. A mRNA molecule is sequentially synthesised by RNA polymerase, as it continues to move along the DNA strand
5. Terminator sequences end the transcription of DNA, and the newly formed mRNA molecule is released.
123
steps involved in translation:
1. mRNA docks to the ribosome
2. The ribosome matches a complementary tRNA molecule to the mRNA by matching codon/anticodon sequences.
3. As subsequent tRNA molecules dock, a polypeptide bond is formed between the adjacent amino acid molecules which they carry.
4. As the mRNA molecule continues to be read, the polypeptide chain is elongated by continued addition of amino acids
5. The polypeptide fold and undergoes post-translational modifications, resulting in a mature protein ready for use in
6. the cell.
124
what is involved in translation?
The genetic sequence of the mRNA molecule is ‘read’ by ribosomes. This code is translated into groups of three nucleotides called a codon.
125
What is translation and what is transcription?
Transcription is literally ‘copying’, you’re using the same basic units (nucleotides) to create an intermediary molecule (RNA)
Translation is actually changing the language. We are turning information stored as nucleotide sequences into amino acid sequences
126
What is the order of processes in creating proteins?
DNA replication
DNA transcription to mRNA
mRNA translates to form proteins
127
What is the importance of mRNA?
Conveys genetic material in DNA to the ribosome
- during translation, each triplet of bases (codon) is used to identify the appropriate anticodon
- mRNA sequence must therefore be accurate for the correct polypeptide to be produced at the ribosome and therefore to maintain healthy cell function
- Hence mRNA is of critical importance in both transcription and translation
128
tRNA- what does the t stand for?
transfer
129
what is the importance of tRNA?
tRNA is responsible for decoding the mRNA as it threads through the ribosome, using the mRNA codon during translation. The corresponding tRNA carries a complementary anticodon which codes for a specific amino acid.
- As the tRNA decodes the mRNA molecule, a chain of amino acids is formed via peptide bonds, which then forms a polypeptide
- Hence, the tRNA molecule is extremely important, as it decodes the mRNA molecule and supplies the appropriate amino acid so that ultimately the correct polypeptide & protein can be formed to maintain cell function.
130
what does polypeptide synthesis do? simple
```
structure and support
transport and storage
enzymes
antibodies
messengers
```
131
polypeptide synthesis- structure and support
Proteins form the basis of the cellular cytoskeleton as well as composing important macro-molecular structures such as connective tissue, hair and nails
132
polypeptide synthesis- transport and storage
Proteins in the cellular membrane are responsible for trafficking molecules into and out of the cell. They may also carry small molecules around the body. Storage proteins reserve important biological materials for use in the body e.g. ferritin stores iron
133
polypeptide synthesis- enzymes
Proteins may function as biological catalysts, carrying out thousands of chemical reactions inside of the cell. Enzymes are used in energy production, DNA replication, transcription and translation
134
polypeptide synthesis- antibodies
Proteins form an important part of the immune response by recognising and binding to foreign particles
135
polypeptide synthesis-messengers
Hormones are proteins which transmit signals around the body, allowing the complex array of biological processes which occur to be coordinated effectively
136
What affects phenotypic expression?
genes and environment
137
how do genes and environment affect phenotypic expression? + example
The appearance of an individual is not solely based on their genetic information. The environment of the organism also plays a part.
e.g.
Hydrangeas are plants that have different flower colours depending on the pH of the soil they are grown in. In acid soil (lower than pH 5) they are blue and in solid that is higher than a pH of 7 they are pink.
The pH has an effect on the availability of other ions in the soil and these ions are responsible for the colour change.
138
what are proteins composed of?
amino acids
139
what are amino acids?
Amino acids are organic compounds which have a central carbon, bound to an amine group, a carboxyl group, a hydrogen and R-group
Amino acids are differentiated by the R-group, which varies in each amino acid and gives the molecule different properties. This then defines the structure and function of the protein overall
140
how do amino acids form polypeptide chains?
Amino acids become parts of polypeptide chains through the formation of polypeptide bonds, which are made between the amine and carboxyl groups in a condensation reaction (this is what occurs in polypeptide synthesis in the ribosome)
141
Primary structure proteins
Primary structures: the sequence of amino acids. The primary structure of proteins refers to the arrangement of amino acid sequences in a polypeptide chain (i.e. the placement of a methionine, next to a proline next to a valine etc) determined by the mRNA code, and formed during translation.
142
secondary structure proteins
the formation of alpha helices and beta sheets. Hydrophobic transactions and hydrogen bonding between amino acid side groups influence the formation of two core structures; alpha helices and beta sheets.
143
tertiary structure proteins
formation of the overall 3D shape. The protein backbone will twist and bend to achieve maximum stability. This. Is facilitated by a side group interaction; for example, disulphide bridges between cysteines, salt bridges between positively and negatively charged side chains, or hydrophobic interactions. The total interactions within the polypeptide chain will result in the formation of a 3D structure.
144
quaternary structure proteins
interaction of protein subunits. Some proteins are composed of multiple polypeptide subunits. The interaction of these influences’ quaternary structure. For example, haemoglobin is composed of four individual subunits, bound together to form the final complex.
145
How do genes and environment affect phenotypic expression?
An individual’s phenotype is a combination of environment and genetic expression.
Nature vs. nurture debate
Some variations are genetically inherited, others are influenced by the environment (and on a wide spectrum)
Variations may arise as a result of interaction: GENES + ENVIRONMENT = PHENOTYPE
146
What did Gregor Mendel do for genetics?
In the 1860’s Mendel formulated the principles of genetics by experimentation with garden peas.
He stated that factors were weaker or stronger not dominant or recessive
147
What are monohybrid crosses?
Involves one factor only
| F2 generation 3:1
148
Homozygous vs Heterozygous genotypes:
Factors that are the same= homozygous
Factors that are different = heterozygous
In the heterozygous condition, the factor that is fully expressed is termed dominant. The recessive factor is masked by the dominant factor.
149
What is the difference between an allele and a gene?
An allele is an alternative form of a particular inheritable characteristic e.g. brown or green
A gene is a section of DNA coding for proteins that expresses itself as the phenotypes of an organism. E.g. eye colour.
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Mendel's first law of dominance and segregation:
Only one number of pair factors can be represented in any gamete (segregation)
Offspring inherit one factor from each parent (modern-day genes)
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Phenotype vs genotype:
Phenotype is the outward appearance of an organism
| Genotype is the actual alleles that are present on the chromosomes of the organism.
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When do Mendellian ratios not apply?
Sex-linked genes and co-dominant genes do not display the phenotype ratios predicted by Mendel's laws.
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How are the 23 chromosomes divided in terms of roles?
22 pairs of autosomes and 1 pair of sex chromosomes in humans
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What do sex chromosome do?
Sex chromosomes carry genes that determine the sexual characteristics of a person and influence whether they are male or female
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Females chromosomes
Females = XX (homogametic)
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Male Chromosomes
Males = XY (heterogametic)
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What chance do offspring have of being male or female?
50/50
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Why do sex linkage characteristics occur?
The X chromosome is larger and may also carry genes for non-sexual body characteristics. These are sex-linked genes as they are physically linked to the sex chromosomes
Females are often carriers, meaning males are more likely to be affected by sex-linkage
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What is co-dominance?
If an individual is heterozygous for a characteristic there are some cases where both alleles are expressed in the phenotype.
Both alleles are labelled with upper case letters
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What is incomplete dominance?
In incomplete dominance, a heterozygous individual blends the two traits
We can still use the mendelian model to predict the results of crosses for alleles that show incomplete dominance
