BIOL1020 Module 5 - Population Genetics

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Department
Biology
Course
BIOL1020
Professor
Dr Paul Ebert
Semester
Spring

Description
Population Genetics DNA and variation Single gene is passed on through time  part of revolutionary process DNA replicates in individuals – evolution happens in populations Selection pressure: a force that causes a particular organism to evolve in a certain direction  Favourable mutation may increase chances of survival Sources of genetic variation 1. Genetic mutation - nucleotide-pair substitution - Silent (synonymous): does not affect amino acid i.e. third position in codon - Missense: altering phenotype - Nonsense: protein no longer created 2. Genetic mutation – nucleotide-pair insertion or deletion - Frameshift causing immediate/extensive nonsense - Insertion of entirely new amino acid 3. Random mutations create allelic variation 4. Recombination and independent assortment in sexually reproducing organs Genetic variation affects individual’s fitness – can be deleterious, neutral or advantageous  Germline (meiosis) mutations matter  Somatic (mitosis) mutations matter to individual but are not heritable (i.e. cancer) Hardy-Weinberg principle (1908) Frequency of alleles and genotypes in a population will remain constant from generation to generation providing:  Only Mendelian segregation applies  Recombination of alleles is occurring Gene pool not evolving assumes:  No mutations  No gene flow  No selection  Random mating  Large population 2 2 Equilibrium = p + 2pq + q Genotype frequency = Allele frequency = Evolutionary processes Evolution: a change in the frequency of alleles over space and time in the gene pool of a reproducing population Allele frequencies change via: 1. New mutations 2. Random chance - Genetic drift – particularly important in small populations - Bottlenecking: portion of population eliminated; population reflects genetics of survivers - Founder effect: genetics reflect those of initial members 3. Non-random mating 4. Gene flow; transfer of alleles - Migration and reproduction Fundamentals of natural selection  Directional selection: change in environm
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