ECCB 400 - Exam 3

estimates of genetic diversity

1. Observed heterozygosity

2. gene diversity

3. nucleotide diversity

observed heterozygosity

number of heterozygotes at a particular locus divided by total number of sampled individuals

Wahlund Effect

• reduction in heterozygosity and excess of homozygotes- leading to a substantial overestimate of He that happens when separate subpopulations with different allele frequencies are combined into single sample

• in presence of effect deviation from HWE can be incorrectly identified

nucleotide diversity

measure of polymorphism in a sample of gene sequences within a population

• reps average # nucleotide differences per site between two DNA sequences chosen randomly from sample population

cost of null allele

• some heterozygote loci will appear as homozygotes, decreasing heterozygosity

null alleles

one that exists in the organism but isn’t detected in assays

What influences genetic diversity

• cqs in ecology, evolutionary biology, and conservation biology

• genetic diversity influenced by a multitude of factors caries significantly between populations

genetic drift

change in population allele frequencies from one generation to the next simply due to chance

Consequences of genetic drift

1. allele frequencies fluctuate from one generation to the next

2. results in nonadaptive evolutionary change, opposite way to natural selection

effective population size (Ne)

• size of idealized that lose genetic diversity through genetic drift @ the same rate as the real population

• smaller than the census population bc not every individual passes on genes

• reflects genetic contribution of each generation to the next

critical endangered consists of population that numbers fewer than

50 mature individuals

Interpreting F_ST

F_ST= 0 two pops have identical allele frequencies

F_ST= 1 two populations are fixed for diff alleles

F_ST= 0-0.05 little differentiation

F_ST= 0.05-0.25 moderate genetic diff

F_ST=0.25 + pronounced genetic variation