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Hardy-Weinberg

Hardy-Weinberg. Using Math. Recall Vocabulary. Allele frequencies - the % of the gene pool that consists of dominant alleles (p) and recessive alleles (q)

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Hardy-Weinberg

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  1. Hardy-Weinberg Using Math

  2. Recall Vocabulary • Allele frequencies- the % of the gene pool that consists of dominant alleles (p) and recessive alleles (q) • Genotype frequencies- the % of the population that consists of homozygous dominant (AA), heterozygous (AB/Aa) and homozygous recessive (BB/aa) individuals

  3. Allele Frequencies Genotype Frequencies p = 6/10 = 0.6 For AA = 2/5 = 0.4 For Aa = 2/5 = 0.4 For aa = 1/5 = 0.2 q = 4/10 = 0.4 AA AA Aa Aa aa

  4. Hardy-Weinberg Equilibrium • If the population is not evolving and p represents the % of alleles that are dominant,then the odds are p that you receive a dominant allele from your mom and p that you receive a dominant allele from your father. • Therefore, the odds are p*p that you will receive a dominant allele from both parents • Thus p2 should represent the % of the population that is homozygous dominant

  5. Example • If 90% of the alleles in a gene pool are dominant, then 81% of offspring should inherit 2 dominant alleles

  6. Summary • p2 = % of population that is homozygous dominant (p 2 = 2 A alleles) • 2pq= % of populations that are heterozygous • Note that both of these genotypes express the dominant trait under complete dominance • p2 + 2pq = % of population expressing dominant trait (unsolvable) • q2= % of population that is homozygous recessive

  7. The 2 “Equations” • p + q = 1 (100% of alleles must be dominant OR recessive) • If you know p, you know q as well • p2 + 2pq + q2 = 1 (100% of individuals must be one of the 3 genotypes)

  8. Careful With Frequencies/% • 1% = 0.01 • 10%= 0.10 • 100% = 1.0 • Square root of 0.01 = 0.1 • Square root of 0.04 = 0.2

  9. Practice • If 10% of the alleles in a gene pool are dominant, what % of the individuals are • Heterozygous? • Homozygous recessive? • Expressing the dominant trait? • If 16% of the population expresses the recessive trait • What are p and q? • What % of individuals are homozygous dominant?

  10. More Practice • 64% of the population expresses the dominant trait • Find p and q and the % of the population that is heterozygous

  11. Another Use of H-W • If p+q=1 and p2 + 2pq + q2 =1, then the population is in equilibrium (isn’t evolving) • If they aren’t, we can tell that the population is in a state of microevolution

  12. Conditions for Equilibrium • The population must be large • The population must be isolated • Each individual must have an equal chance of surviving • Each individual must have an equal chance of reproducing (no selecting mating) • There must be no mutations

  13. *A Note on the AP Test • The 2012 AP Bio test will involve math, calculators, and grid-in answers • So you can get H-W problems that do not involve perfect squares • You need to be careful not to make silly mistakes

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