Population Genetics (L19-21) Flashcards

1
Q

Heterozygosity

A

frequency of heterozygotes

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2
Q

Genotype frequency

A

number of individuals with genotype/total individuals

So all frequencies add to 1

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3
Q

Allele frequency

A

Number of allele present/total allele

So all allele frequencies add to 1

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4
Q

Assumptions of population genetics

x 4

A
  1. diploid organisms
  2. Non-overlapping generations
  3. Autosomal loci
  4. Random mating
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5
Q

Hardy Weinberg assumptions - therefore some of the assumptions of population genetics

x 8

A
  1. Random mating
  2. No selection
  3. No migration
  4. No mutation
  5. Non-overlapping generations
  6. Autosomal locus
  7. Infinite population size
  8. Diploid organisms
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6
Q

Allele lottery

A

the idea that the allele frequency in next gen under genetic drift is going to be subject to stochastic sampling

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7
Q

Homozygosity

A

The frequency of homozygotes - tending to homozygosity means tending towards all being homozygotes

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8
Q

Using effective population size, what is a large population and what is a small population

A

large is Ne of >10,000

small is <100

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9
Q

genetic differentiation

A

a difference in allele frequency between subpopulations due to genetic drift causing allele frequency divergence

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10
Q

Wahlund effect

A

The deficiency of heterozygotes compared to HWE when summing across subpopulations

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11
Q

Fixation index

A

the proportional difference between expected heterozygosity in the total population and actual heterozygosity in total population

  • also known as
    proportion of genetic variance in subpop relative to total pop
  • level of inbreeding in subpop compared to total pop
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12
Q

Inbreeding

A

Homozygosity for alleles that are identical - by - descent (idb)

= autozygosity

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13
Q

What is F

A

The inbreeding coefficient = the probability that two randomly drawn alleles are ibd

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14
Q

mating system inbreeding

A

non-random mating among relatives, regardless of population size

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15
Q

What does μstand for?

A

the constant rate of mutation per locus per generation

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16
Q

What happens if fitness is random with respect to genotype?

A

No selection occurs

17
Q

Absolute measurement of fitness

A

average total number of surviving offspring for a genotype

18
Q

Relative fitness

A

fitness compared to another genotype - easiest to compare difference in fitness

19
Q

What do we ignore when using relative fitness

A

changes in population size

20
Q

2 different components of fitness

A
  1. survival to adulthood

2. fecundity

21
Q

What is fecundity

A

the reproductive output of an individual

  • usually the maximum
  • combines gamete production and mating sucess
22
Q

what is s

A

the selection coefficient - or selection differential

23
Q

3 x origins of adaptive alleles

A
  1. new mutation - like melanism in peppered moths or insecticide resistance
  2. Standing genetic variation - so already there but was neutral or deleterious - repeatability of evolution with sticklebacks
  3. Adaptive introgression
24
Q

What is the major consequence of inbreeding

A

inbreeding depression

25
what is inbreeding depression
a reduction in fitness of a population due to inbreeding
26
Mating system inbreeding
leads to higher visibility of deleterious alleles to selection - as more homozygote recessive
27
Overdominance
heterozygote advantage
28
2 types of balancing selection
1. Overdominance = rare | 2. frequency dependence
29
what is r
the recombination fraction
30
what is the recombination fraction
number of offspring that inherit different alleles of a trait from each parent
31
what is r maximum
0. 5 | - when no linkage of alleles
32
what is r<0.5
is r is less than 0.5 then linked loci
33
causes of linkage disequilibrium x 2
1. gene flow among populations - with different allele frequencies 2. selection for allelic associations - so certain combinations have higher frequency
34
Chromosomal inversions
rearrangement produced by two breakages and inverts the gene on a chromosome
35
Supergene
when multiple gene loci accumulate and are inherited together due to chromosomal inversion
36
what affects the size of the region of neutral variation at linked sites due to directional selection at one locus
the recombination rate near selected locus
37
what is a selective swap
directional selection at a locus causes a loss of neutral variation at linked sites
38
how to escape a local optimum - Wright
recombination mutation genetic drift
39
fate of a favourable allele depends on 8 things | what are they?
1. selection differential s 2. initial frequency (especially if allele only now favourable) 3. Population size - determines drift 4. dominance relationships 5. presence of frequency dependence 6. temporal variation in s 7. presence of gene flow with a population where allele absence or not under selection 8. Linkage - to other favourable or unfavourable