BIOLOGY 1114H Lecture Notes - Lecture 4: Zygosity, Allele Frequency, Genetic Drift
6 Sep 2016
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Department
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Bio1114H
Lecture 4
Mitochondrial DNA
Extranuclear DNA inherited solely from mother that evolves relatively slowly compared
to other genetic markers
Assumptions of Hardy Weinberg Equation
No mutation
No migration
Large population size
Random mating
Hardy Weinberg isn’t realistic model because evolution is always happening and the
equation is a null hypothesis. If it is accepted, no evolution. If it is rejected, evolution is
occurring
1. No mutations: mutations are random and result in new variations and are rare and
usually non-adaptive.
2. No migration (no gene flow)
3. Large Population Size because with small populations, genetic drift occurs more
significantly, as well as continuous and intermittent effects (seasonality,
bottlenecking, founder effects)
4. Random mating because if non-random, inbreeding/self-fertilization; assortative
mating. This can lead to polarized populations, decreased heterozygosity and
inbreeding depressions
5. No selection which includes changes in genotype and allele frequencies, non-
random adaptive which brings fitness into play. This can be disruptive, directional,
stabilizing, or sexual
Hard vs. Soft selection
Hard: selective pressure constant, effect primarily on survival
Soft: pressure on survival and reproductive success
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Document Summary
Extranuclear dna inherited solely from mother that evolves relatively slowly compared to other genetic markers. Hardy weinberg isn"t realistic model because evolution is always happening and the equation is a null hypothesis. If it is rejected, evolution is occurring: no mutations: mutations are random and result in new variations and are rare and usually non-adaptive, no migration (no gene flow) Large population size because with small populations, genetic drift occurs more significantly, as well as continuous and intermittent effects (seasonality, bottlenecking, founder effects: random mating because if non-random, inbreeding/self-fertilization; assortative mating. This can lead to polarized populations, decreased heterozygosity and inbreeding depressions: no selection which includes changes in genotype and allele frequencies, non- random adaptive which brings fitness into play. This can be disruptive, directional, stabilizing, or sexual. Hard: selective pressure constant, effect primarily on survival.
