Population genetics

population genetics

study of inherited variation between populations over time and space

gene frequency

allele frequency in a population

population

local group of a species among which mating can occur

Allele and genotypic frequencies will arrive at and remain at equilibrium frequencies

after one generation of random mating if all assumptions are met

What is hardy weinburg equilibrium

p² AA+ 2pq Aa + q² aa

What assumptions must be met in hardy Weinberg

infinitely large population, random mating, no selection, no migration, no mutation

Degrees of freedom for hardy weinberg chi square is

number of genotypes - number of alleles

F(M) +

F(N) = 1

Fitness is the

ability to survive and reproduce

direction selection (additive effects)

AA is closest to 1 with BB lowest

disruptive selection (underdominance)

heterozygote is lowest

stablizing selection (overdominance)

BB is lowest while AB IS HIGHEST

What kind of selection favors the heterozygotes?

stabilizing selection

What kind of selection favors a bimodal population?

disruptive selection

genetic drift

random loss and fixation of alleles

founder population

small population that colonizes a new area

inbreeding

mating between relatives is more likely in a small population, resulting in .

assortive mating

mate based on phenotype

Positive assortative mating:

mating like individuals together, results in more

homozygotes, but only for loci under selection.

Negative assortative mating:

“opposites attract” would keep diversity in the

population and results in more heterozygotes for the loci under selection.

What are the effects on inbreeding

mating of related individuals changes frequency of

genotypes, but not allele frequency and leads to more homozygotes in

population over time. Affects all loci in the organism.

Non-Random mating changes frequency of genotypes but not

allele

frequency.

inbreeding results in more

Homozygotes

F is the

inbreeding coeffieceint

F=0

no inbreeding

0 < F < 1

inbreeding occurs

If inbreeding is occurring then

(p²+Fpq)AA+ 2(1-F)pq Aa +(q² +Fpq) aa

inbreeding does not

alter allele frequncies

migration

a change in gene frequency depends on migration rate and on the gene frequency of the immigrants vs native

P

frequency of A allele in the donor population (mainland).

m

proportion of migrants after immigration occurred = probability that

a parent will come from the mainland.

p

= frequency of A allele on island initially.

1 - m

probability that a parent will come from the island = proportion of

total population after migration that was from the island.

p’

frequency of A allele after migration.

p’ formula =

(1-m)p + mP