Population Genetics - Hardy-Weinberg

Genotype frequencies

They add up to 1 and remain constant unless affected by selection

Allele frequencies

They add up to 1 and remain constant unless affected by selection

Why do allele frequencies always add up to 1?

Because there are only two alleles at the locus

Frequency of the a allele

A = all of the AA + ½ of the Aa, a = all of the aa + ½ of the Aa

Frequency of the aa genotype

The frequency of the aa genotype is q * q

Hardy-Weinberg assumptions

Infinitely large population, random mating with respect to the locus, and two alleles at the locus

Predictions if all HWE assumptions are met

Allele frequencies remain constant, and expected genotype frequencies can be calculated

Expected genotype frequencies in the next generation

Calculated using the Hardy-Weinberg equations

Hardy-Weinberg Equilibrium

A state where allele frequencies remain constant from generation to generation

Equilibrium

A state where things remain stable over time

Hardy-Weinberg equations

p p for AA, 2pq for Aa, and q q for aa

Implications of the Hardy-Weinberg Principle

Allele frequencies remain constant, and sexual reproduction does not change allele frequencies

Expected frequency of the AA genotype

p * p for a population at Hardy-Weinberg equilibrium

Expected frequency of the Aa genotype

2pq for a population at Hardy-Weinberg equilibrium

Number of A alleles in the population

251 (from AA) + 0.5 * 25 (from Aa)

Number of a alleles in the population

11 (from aa) + 0.5 * 25 (from Aa)

Frequency of the A allele in the population

(251 + 0.5 * 25) / (251 + 25 + 11)

H-W expected frequency of the AA genotype

p * p for a population at Hardy-Weinberg equilibrium

H-W expected frequency of the Aa genotype

2pq for a population at Hardy-Weinberg equilibrium

H-W expected frequency of the aa genotype

q * q for a population at Hardy-Weinberg equilibrium

Expected frequency of the aa genotype in the next generation

0.00672 for p = 0.918 and q = 0.082

Expected frequency of the Aa genotype in the next generation

0.15 for p = 0.918 and q = 0.082

Expected frequency of the AA genotype in the next generation

0.84 for p = 0.918 and q = 0.082