Biology 3201 Evolution

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Biology 3201 - Evolution

• Evolution in Action
• Hardy-Weinberg law

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Hardy-Weinberg Law (set up)

• Population Genetics - The study of allele
  frequencies within a population
• Gene Pool - All of the genes of a population of
  organisms (Organisms that are successful at
  reproducing contribute most to the gene pool).
• Species - a group that have the potential to
  interbreed and produce fertile offspring

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Hardy-Weinberg Law

• Evolution - can be any change in the frequency of
  any allele within a gene pool (populations
  undergo evolution but individuals do not undergo
  evolution, they under go selection).
• The Hardy-Weinberg law examines changes in gene
  pools and explains how evolution can select for
  certain genes

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Hardy-Weinberg Law

• Hardy-Weinberg theorem only applies to a
  population in HW equilibrium.
• HW equilibrium has the following
• Large Population
• No Mutations
• No Migration or Emigration
• No Selection of Alleles
• Random mating

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• Theorem p q 1 Where p the frequency of the
  dominant allele and q the frequency of the
  recessive allele
• All the alleles in a population will total 100
  (or 1 in this case)
• p2 2pq q2 1 p2 homozygous dominant
  2pq heterozygous q2 homozygous
  recessive
• This determines the genotype frequencies in a
  population at HW equilibrium.
• Note that the square root of p2 p and the
  square root of q2 q

6

• Try this If a population has a dominant allele
  found at a frequency of 90. What are the
  percentages of homozygous dominant, heterozygous
  and homozygous recessive individuals in the
  population?
• The p 0.9 Thus q 0.1 now use the formula to
  get the rest - p2 2pq q2 1
• homozygous dominant p2 or 0.81 or 81
• heterozygous 2(0.90.1) 0.18 or 18
• homozygous recessive q2 or 0.01 or 1
• Total 100, note that the dominant allele does
  not eliminate the recessive allele