Genetic Diversity Flashcards
1
Q
Define genetic diversity
A
The total number of alleles in a population
2
Q
Define population
A
A group of individuals of the same species that live in the same area at the same time and can interbreed
3
Q
What does a species consist of?
A
One or more population
4
Q
How can you increase the genetic diversity of a species?
A
Increase the number of different alleles that a species possesses
5
Q
The greater the genetic diversity…
A
The more likely that some individuals in a population will survive an environmental change
6
Q
What is selection?
A
The process by which organisms that are better adapted to their environment tend to survive and breed, while those that are less adapted tend not to
7
Q
What does directional selection do?
A
Changes the characteristics of a population
8
Q
What does stabilising selection do?
A
Preserves the characteristics of a population
9
Q
How does stabilising populations preserve the characteristics of a population?
A
Because it eliminates phenotypes at the extremes and favours those at the mean
10
Q
How does directional selection work?
A
If environmental conditions change, the phenotypes that are best suited to the new conditions are more likely to survive.
(These are often the phenotypes at the extremes)
11
Q
Natural selection results in…
A
Species that are better adapted to then environment they live in.
12
Q
What adaptations may be caused as a result of natural selection?
A
Anatomical (eg shorter ears)
Physiological
Behavioural
13
Q
What’s the concept of a species?
A
They are capable of breeding to produce living, fertile offspring
14
Q
Define intraspecific variation
A
Differences in organisms within the same species
15
Q
Describe continuous variation
A
- strongly influenced by the environment
- no distinct categories
- tends to be quantitative
- controlled by a lot of genes
16
Q
Describe discontinuous variation
A
- unaffected by the environment
- controlled by only a few genes
- distinct categories
- tends to be qualitative
17
Q
Why is standard deviation a good measure?
A
It takes into account the spread around the mean.
If a high proportion of data points lie near the mean value then the standard deviation is small and vice versa
18
Q
What is a mutation?
A
A change in the nucleotide (DNA) base sequence
19
Q
How could a mutation affect a protein molecule so that it cannot function?
A
Because it affects the tertiary shapes
20
Q
Why are mutations that affect large sections of DNA lethal?
A
Because the protein is expressed
21
Q
What is a base substitution?
A
The replacement of one nucleotide with another containing a different base
22
Q
Define deletion?
A
The loss of a nucleotide (also fled a frame shift mutation)
23
Q
A mutation may have no mutation. Why?
A
- it occurs on a non-coding region of DNA
- a different codon may produce the same amino acid (degenerate)
- he altered amino acid may not affect the protein’s shape of function
24
Q
How do mutations arise? (2)
A
Spontaneously through DNA replication when a cell divides by mitosis or meiosis
By mutagenic agents
25
How does homologous chromosomes create genetic diversity?
Because an organism inherits one member of each homologous pair of chromosomes from your mother (MATERNAL CHROMOSOME) and the other pair from your father (PATERNAL CHROMOSOME).
The fusion of these gametes in sexual reproduction produces genetic diversity because each parent may contribute different alleles.
26
Define diploid.
A cell with pairs of homologous chromosomes.
27
Define haploid.
A cell with only one chromosome from each homologous pair.
28
Are gametes diploid or haploid?
Haploid.
29
What produces haploid cells from diploid cells?
Meiosis
30
How does meiosis produce haploid cells that are genetically different from each other?
Because of genetic recombination by crossing over and the independent assortment of homologous chromosomes.
31
In the independent assortment of homologous chromosomes, what happens in the first meiotic division?
The chromosomes are separated into each homologous pair. (Eg the maternal chromosome from one pair would move to one side of the cell).
32
What is the result of the first meiotic division in the independent assortment of homologous chromosomes?
Gametes will contain a mixture of maternal and paternal chromosomes.
33
In the independent assortment of homologous chromosomes, what does the second meiotic division do?
It separates the 2 chromatids that were made by DNA replication before mitosis started.
34
What happens in crossing over?
During the first meiotic division, the members of each homologous pair lie side by side. If chromatids be me tangled with one another, they may break and the broken segments may be rejoined to chromatids in opposite members of the pair.
35
What does crossing over lead to?
It results in recombination.
| A new combination of alleles that gives rise to genetic diversity.
36
What is a chromosome mutation?
A change in the number of chromosomes
37
What is non-disjunction?
When chromosomes fail to separate properly during meiosis, then a gamete ends up with two copies of a chromosome rather than one.
That gamete would contain one more than the haploid number and in fertilisation would result in a chromosomes mutation.
38
Define gene mutation.
A change in the base sequence of a gene, forming a new version of the gene or allele.
39
When does gene mutation generally occur?
When DNA is replicated.
40
How often does a gene mutation occur?
Around once in every 1 million times a gene is copied.
It is completely RANDOM and SPONTANEOUS.
41
What is a neutral mutation?
A gene mutation that causes a change in the sequence of amino acids in the encoded protein but has no effect on the function of the protein.
42
How can a gene mutation be harmful?
When a gene mutation causes a change in the amino acid sequence of the encoded protein and its function is lost.
43
What happens if a gene mutation produces a beneficial change in the activity of the encoded protein?
The individual in which the mutation ha scoured has an advantage over other members of the population. This can lead to the mutation being passed on, or inherited, by its offspring.
44
What are the two types of gene mutation?
- base deletion
| - base substitution
45
What happens in a base deletion?
A base is lost from its base sequence.
46
In base deletion, what is a frame shift?
When the whole base sequence following the deleted base moves back one place.
47
Why does a base deletion have a significant effect on the encoded protein?
Because it can alter the sequence of all of the codons following the lost base.
48
What is base substitution?
The wrong base is included in the base sequence.
49
What is the bad outcome of base substitution?
It may result in a different amino acid being included in the polypeptide chain.
50
When is the good outcome of a base substitution?
The substitution may result in a triplet that still codes for the same amino acid, so the sequence of amino acids will stay the same because the genetic code is degenerate.
51
Define degenerate.
Several mRNA codons may encode for the same amino acid.
52
What is a mutagenic agent?
An environmental facto that increases the rate of mutation.
53
Name 3 mutagenic agents.
- toxic chemicals (eg peroxides)
- ionising radiation (eg x-rays)
- high energy radiation (UV light)
54
When a gene mutates, it has two forms. What are they?
The original form and the mutated form.
55
What is an allele?
Different forms of the same gene.
56
When talking about natural selection, why should you refer to alleles rather than genes?
Because a gene is for the character (eg shell colour). But alleles are the different forms of the gene that control the pink and yellow colours.
57
What is natural selection?
When a gene mutates, if one of the alleles of the gene confers an advantage over the alternative allele of the same gene, its frequency will rise in the population.
58
What is an advantageous allele?
An allele that confers an advantage over the alternative gene in natural selection.
59
What does natural selection do?
It changes the frequency of alleles in a population of a species, including in populations of humans.
60
Allele frequencies in a large population generally remain stable from generation to generation. However this will not be true if some organisms are...
- more likely to survive until they reproduce
- more likely to attract a mate
- more likely to grow sufficiently well to reproduce successfully
61
What does 'increased reproductive success' mean?
When the environment changes (or new advantageous alleles arise by mutation), some organisms will tend to reproduce more successfully than others and leave more offspring.
62
What is directional selection?
When natural selection through gene mutation results in the frequency of an advantageous allele increasing in the gene pool.
As a result, one allele become rare whilst the other becomes common.
63
What is stabilising selection?
Natural selection resulting in unfavourable alleles becoming rare in the gene pool.
64
How does stabilising selection work?
It acts against the extreme phenotype in a population (for example an extremely light or extremely heavy birth weight).
If some phenotype are more optimal then the frequency of these allele for these phenotype remains the same whilst other forms that are disadvantaged are reduced.
65
What is antibiotic resistance?
Some bacteria (such as those that cause TB) have already evolved resistance to a range of antibiotics.
66
How does natural selection explain antibiotic resistance in bacteria?
Take antibiotic.
Initially, none of the bacterial cells are resistant to the antibiotic.
By chance, a mutation occurs which results in an allele that gives resistance to an antibiotic to the bacteria whom possess it (so they have an advantageous allele).
The cells without mutation (the susceptible cells) are killed by the antibiotic whilst the cell carrying the mutation survives and reproduces successfully.
The resistance allele is passed on to more offspring and the frequency of this allele will be greater in the population in the next generation than it was in the parental generation.
67
What factors caused variation?
Environmental and genetic factors.
68
Why might a sample not be representative of the population?
Chance
| Sampling bias
69
How can you reduce the effect of chance being unrepresentative of the population?
By taking several samples and finding their average value.
70
Explain sampling bias as a factor that is unrepresentative of the population.
This happens when the investigator, knowingly or unknowingly, chooses which measurements to include in the same.
71
How can you reduce the effect of sampling bias being unrepresentative of the population?
By using a random sampling technique.
This is a technique of selecting the individuals in a sample and removes the investigators choice. This ensures the measurements are representative if the whole population and not affected by bias.
72
What is standard deviation?
A measure of the spread of data around the mean value.
73
In standard deviation, why is it good if the results show little variation?
Because the results are more precise.
74
In standard deviation, give an example of less precise results.
When the results show too much variation.
(For example, calculation the mean time for an enzyme controlled reaction to finish, with the end times being 25, 45 and 65 seconds and they all give the same mean time).
75
In standard deviation, what does a narrow spread of measurements mean?
The measurements in the sample were very similar. It has a small standard deviation.
76
How to find the scientific name?
The name of..
| Genus, species
77
To find the scientific name of an organism you do the genus then species. Where are the capital letters located?
Genus has a capital letter
| species has a lower case letter.
78
What is genetic diversity?
The number of different alleles in a species / population.
79
In general, what does natural selection do?
Natural selection acts to increase the proportion of advantageous alleles.
80
What increases genetic diversity?
- mutations in the DNA; forming new alleles.
- new alleles being introduced into a population; when individuals from another population migrate into them and reproduce.
81
Genetic bottlenecks __________ genetic diversity.
Reduce
82
What is the founder effect?
1. Geographical isolation / separation in a population eg due to religion.
2. A few organisms from a population start a new colony, and there are only a small number of different alleles in the initial gene pool.
3. The frequency of each allele may be very different to that in the original population - an allele rare in the original population may become common in the new colony (may lead to higher incidence of genetic disease).
83
In what ways can natural selection lead to populations becoming better adapted?
- behavioural (eg actions like playing dead in front of predator)
- anatomical (eg hibernation reduces rate of metabolism)
- physiological (eg thick layer of blubber)
84
What is directional selection?
Where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce.
Eg antibiotic resistance.
85
What is stabilising selection?
Where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce. It reduces the range of possible characteristics. Eg human birth weight.
86
What are phylogenetic trees?
A graph to show how all organisms have evolved from shared common ancestors.
87
Order of taxonomy?
Domain, kingdom, phylum, class, order, family, genus, species
88
Outline how the binomial naming system works in classification.
The genus is stated first, with a capital letter. The species next with lower case.
89
Define courtship behaviour.
Courtship behaviour is carried out by organisms to attract mates of the right species (it's species specific). Eg series of displays, or releasing chemicals.
90
Why is courtship behaviour used?
It allows members of the same species to recognise each other, prevent interbreeding and malign reproduction more successful (as mating with the wrong species doesn't produce fertile offspring).
91
What are the 3 techniques used for clarifying evolutionary relationships?
- comparing amino acid sequence
- genome sequence
- immunological comparison
92
Evolutionary relationships can be clarified by comparing amino acid sequences. How does this work?
The sequence of amino acids in a protein is coded for by the base sequence of DNA. Related organisms have similar DNA sequences - so similar amino acid sequences in their proteins.
93
Evolutionary relationships can be clarified by genome sequencing. How?
In genome sequencing, the entire base sequence of an organism's DNA can be determined. This DNA base sequence of one organism can then be compared to the DNA base sequence of another organism to see how closely related they are.
Closely related organisms will have a higher % of similarity in the DNA base order.
94
Evolutionary relationships can be clarified using immunological comparisons. How?
Similar proteins bind to the same antibodies.
Eg if antibodies to a human version of a protein are added to isolated samples from another species, any protein that's like the human version will be recognised by that antibody.
