Population genetics Flashcards
1
Q
define evolution:
A
- change of allele frequencies over time
2
Q
what causes change to allele frequencies:
A
- natural selection
- genetic drift
3
Q
natural selection:
A
- organisms best suited to environment have more resources for survival and reproduction
4
Q
fitness:
A
- relative genetic contribution of individual to next generation
- successful alleles individuals carry passed on
5
Q
adaptation:
A
- change in populations through natural selection
6
Q
directional selection:
A
- individuals with traits at one extreme favoured over another
7
Q
stabilising selection:
A
- individual with intermediate traits favoured
8
Q
disruptive selection:
A
- individuals from either extreme favoured
9
Q
eg. directional selection
A
- herbicide application
- many plant species evolving with resistance
- also antibiotic resistance in hopsitals
10
Q
genetic drift:
A
- change in allele frequencies across generations due to chance events
11
Q
list chance events:
A
- random disturbances
- small populations
- Founder effects
12
Q
population size:
A
- genetic drift more likely to occur in small populations
= fixation of allele and loss of others - less likely in large populations, random events are buffered
13
Q
Founder effect:
A
- individuals disperse to new area, subset of alleles from entire population
- large change in allele frequencies
- inbreeding
14
Q
bottleneck effect:
A
- rapid decrease in population size due to disturbance or natural disaster
- removes individuals with some alleles from population
- those which survive alter gene frequencies
15
Q
eg. Pingelap
A
- island of colourblind
- 10% individuals completely colourblind in population
- 1775 population reduced to 20 people due to typhoon
- bottleneck effect
- all colourblind people can be traced back to one person with recessive genetic disorder
16
Q
significance of Pingelap:
A
- random disturbance initially changed allele frequencies
- bottleneck left small founding population
- random chance + small population size + inbreeding = allele not adaptive have high frequency in population
17
Q
gene flow:
A
- allele moves btw populations
- can increase genetic variation
- decrease effects of genetic drift
- can lead to homogenisation across populations
- dilute effects of localised natural selection and adaptation
18
Q
population:
A
- individuals of species which interbreed with each other but not w individuals of same species of another population
- different populations becomes more genetically differentiated
- over long periods of time, no genetic exchange will evolve into different species
19
Q
gene pool:
A
- entire genetic content of population
- every allele
- we only study specific alleles
20
Q
mutations:
A
- change in DNA sequence
- error in DNA replication
- caused by mutagens
- most mutations are deleterious, but some create alleles that increase fitness
21
Q
sexual reproduction:
A
- new combinations of alleles produced
- recombination of alleles in meiosis
22
Q
Hardy-Weinberg equilibrium:
A
- when allele and genotype frequencies remain constant from gen to gen, population is not evolving
- only Mendelian segregation and recombination of alleles at work
- this type of population: Hardy-Weinberg equilibrium
23
Q
how to determine offsprings in Hardy-Weinberg equilibrium:
A
- consider combo of alleles in all crosses in population (genotype and allele frequencies)
- will add up to 1 (100%)
24
Q
Hardy-Weinburg equilibrium: equation
A
- at locus with 2 alleles
- 3 genotypes will appear:
p2 + 2pq + q2 = 1
25
result of not meeting 1 of 5 conditions of Hardy-Weinberg equilibrium:
1. no mutations
2. random mating
3. no natural selection
4. extremely large population size
5. no gene flow
- allele and genotype frequency will change
- real populations change over time
26
evolution:
- change in allele frequencies btw generations
27
to calculate genotype frequency:
no. of individuals with specific genotype ÷ no. of total individuals
28
to calculate allele frequency:
no. of particular allele ÷ total no. of alleles in all individuals
29
how many genotypes per individual?
one
30
how many alleles per individual?
two
| - one per chromosome of every individual