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2010-11-28 16:57:29
Bio115 lecture36

Bio115 lecture 36
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  1. Hardy-Weinberg Law: Comparing Genotypic exp with freq
    • 1. Calculate the allelic frequencies
    • 2. Find the expected genotypic frequencies
    • 3. Compare the observed and expected genotypic frequencies using a chi-square test
  2. How do you calculate the degrees of freedom for the Chi-Square test in Hardy-Weinberg proportions?
    In general, the degrees of freedom for a chi-square test of Hardy-Weinberg equilibrium equal the number of expected genotypic classes minus the number of associated alleles
  3. Positive assortative mating
    Tendency for individuals sharing a particular trait to mate
  4. Negative assortative mating
    Tendency for individuals that do not share a particular trait to mate
  5. Inbreeding
    Preferential mating between related individuals
  6. Outcrossing
    Avoidance of mating between related individuals
  7. How does inbreeding affect homozygosity and allele frequencies?
    Inbreeding leads to an increase in homozygosity at all loci, but no change in allele frequencies
  8. Inbreeding depression
    The increased appearance of lethal and deleterious traits with inbreeding
  9. Processes that bring about change in allelic frequency
    • Mutation
    • Migration
    • Genetic Drift
    • Natural selection
  10. Genetic Drift
    Sampling error/random effects due to small population size
  11. What are the overall affects of migration?
    • Gene pools of populations become more similar
    • Increases genetic variation within the recipient population
  12. Genetic drift results in...
    the divergence of populations and often results in one allele becoming fixed
  13. What are two causes of genetic drift?
    • Founder Effect
    • Genetic bottleneck
  14. Three related effects of genetic drift are:
    • 1. Change in allelic frequency
    • 2. Reduced genetic variation
    • 3. Different populations diverge genetically with time
  15. Natural Selection
    The differential reproduction of genotypes when individuals with adaptive traits produce a greater number of offspring than that produced by others in the population
  16. Fitness
    The reproductive success of one genotype compared with the reproductive successes of other genotypes in the population
  17. Calculating fitness (W)
    Divide the mean number of offspring produced by a genotype by the mean number produced by the most prolific genotype
  18. Selection coefficient (s)
    The relative intensity of selection against a genotype
  19. Calculating the selection coefficient
    s = 1 - W
  20. General Selection Model
    know table 25.4
  21. Three Different types of selection
    • Selection against a dominant allele is very efficient
    • Selection against an autosomal recessive allele is inefficient
    • Balancing selection where the heterozygous genotype is most fit
  22. Do problem on slide 21
    calculate relative fitness and next generation frequency of an allele
  23. Mutation's long-term effect on allelic frequency
    Equilibrium reached between forward and reverse mutations
  24. Migration's long-term effect on allelic frequency
    Equilibrium reached when allelic frequencies of source and recipient population are equal
  25. Genetic drift's long-term effect on allelic frequency
    Fixation of one allele
  26. Natural Selection's long-term effect on allelic frequency
    • Directional selection: fixation of one allele
    • Overdominant selection: equilibrium reached