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Hardy-Weinberg Equilibrium

Hardy-Weinberg Equilibrium. Honors Biology. Is evolution occurring right now?. How might a scientist tell if evolution is occurring within a population?. Use the Hardy Weinberg Equation!. Review Mendel’s work. Organisms have 2 alleles for each trait Only 1 can be passed to offspring

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Hardy-Weinberg Equilibrium

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  1. Hardy-Weinberg Equilibrium Honors Biology

  2. Is evolution occurring right now? • How might a scientist tell if evolution is occurring within a population?

  3. Use the Hardy Weinberg Equation!

  4. Review Mendel’s work • Organisms have 2 alleles for each trait • Only 1 can be passed to offspring • This passing is requires alleles to separate in meiosis in a random fashion

  5. Gene Pools • Collection of alleles within a population • Ex: 1,000 cats • Black (B) is dominant to white (b)

  6. Allele Frequency • If governed by complete dominance, • EX: 1,000 cats • BB – black (360) = 36% • Bb – black (480) = 48% • Bb – white (160) = 16%

  7. Lets do some math • With two alleles per cat, there are 2,000 alleles in the population • If there are: • 360 black (AA) = 720 B alleles • 480 black (Aa) = 480 B alleles & 480 b alleles • 160 white (aa) = 320 b alleles

  8. Allele frequencies: • 1200 / 2000 B alleles exist (60% or 0.6) • 800 / 2000 b alleles exist (40% or 0.4)

  9. If evolution is not occurring, • The allele frequencies will not fluctuate over time • Population is said to be at Hardy-Weinberg Equilibrium (HWE)

  10. H.W.E. Conditions • Very large population size • Isolation from other populations • No Mutations • Random Mating • No natural selection

  11. Applying H.W.E. • p represents the dominant allele • q represents the recessive allele p + q = 1 0.6 B alleles + 0.4 b alleles = 1

  12. Solve this story problem • In certain Native American groups, albinism is due to a homozygous recessive condition. If the frequency of the allele for this condition is 0.06, what is the frequency of the dominant allele in this population? p + q = 1 P + .06 = 1 p = .94

  13. Applying H.W.E. • (p + q) X (p + q) = p2 +2pq + q2 Male gametes Female gametes genotype frequencies in next generation

  14. Applying H.W.E. • p2 = homozygous dominant condition • 2pq = Heterozygous condition • q2 = homozygous recessive condition p2 +2pq + q2 = 1 BB + 2Bb + bb = 1

  15. Solve this story problem • In a certain flock of sheep, 4 percent of the population has black wool and 96 percent has white wool. • If black wool is a recessive trait, what percentage of the population is heterozygous for this trait? p2 +2pq + q2 = 1 p + q = 1

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