Mating

Random mating

  • Potential mates are equally likely


Non-Random Mating

  • Potential mates are NOT equally likely

  • Influenced by genotype or phenotype

Assortative: similar individuals more likely to mate

  • Results in more homozygotes

Disassortative: Dissimilar individuals are more likely to mate

  • Results in more heterozygotes

Non-random mating VIOLATES assumption of HWE

NRM changes genotype frequencies

  • Does not directly change allele frequencies

  • Thus, not a mechanism of evolution directly


Inbreeding

Inbreeding as a nonrandom assortative system of mating will lead to

  • higher homozygotes


Selfing: mating with yourself

  • Fairly common in plants

  • Some hermaphroditic animals too


Inbreeding: loss of heterozygosity

Inbreeding + Selection: increase in homozygosity exposes recessive deleterious alleles to selection

Inbreeding depression: the reduction in fitness due to inbreeding


Measuring inbreeding- coefficients

  1. Pedigree Inbreeding

    • About the individual

  2. System-of-Mating Inbreeding

    • How inbred is the population?

    • Based on deviations from HWE

    • Ho much has inbreeding reduced heterozygosity in the population

    • F = 1 - (f(Aa) / (2pq)

    • = 1 - (Obs / Exp)

    • Interpreting F

      • F > 0 → inbreeding; Homozygote excess

      • F = 0 → random mating

      • F < 0 → inbreeding avoidance; Heterozygote excess