Population Genetic

• Hardy-Wienberg Law• Genetic drift• Inbreeding• Genetic Bottleneck• Outbreeding• Founder event• Effective population size• Gene flow

Population Genetics

• Genotype, phenotype

• locus, genotype frequency, allele frequency

Determining the genotype for an enzyme in a fish.

IDHP (isocitrate dehydrogenase) from a grasshopper

Individuals

1 2 3 . . .

AA

aa

Aa

Genotype and Phenotype• Genotypes AA, aa (Homozygous), Aa (Heterozygous)• Phenotype trait X = AA and Aa , trait Y = aa• Alleles A and a

• If p = proportion of allele A and if q = proportion of allele a• Then p+q = 1• Knowing p and q the Hardy-Wienberg Equilibrium gives the

expected frequency of the three genotypes as:

• (p+q)2 = p2 +2pq + q2 = 1 AA = p2, aa = q2 and Aa = 2pq

Hardy-Wienberg EquilibriumAssumptions

• Population size is very large• Random mating is occurring• No mutation is taking place• No immigration (geneflow)• No selection is occurring

Genetic drift

Inbreeding

A alleles common by descent

• Effective population size• Founder effect• Genetic bottleneck• Outbreeding depression• Gene flow