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Hardy-Weinberg and Genetic Equilibrium

Hardy-Weinberg and Genetic Equilibrium. Page 400. A. Hardy-Weinberg Principle. 1. States that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change. A. Hardy-Weinberg Principle.

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Hardy-Weinberg and Genetic Equilibrium

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  1. Hardy-Weinberg and Genetic Equilibrium Page 400

  2. A. Hardy-Weinberg Principle • 1. States that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change.

  3. A. Hardy-Weinberg Principle • 2. When allele frequencies remain constant, that is called genetic equilibrium (no evolution).

  4. B. Five Conditions • 1. There must be random mating. • 2. The population must be very large.

  5. B. Five Conditions • 3. There can be no movement in or out of a population.

  6. B. Five Conditions • 4. No mutations. • 5. No natural selection.

  7. C. Solving Problems • 1. Imagine a geneticist studies a trait with alleles A and a.

  8. C. Solving Problems • 2. A is dominant and a is recessive. A survey shows 4% of the population has aa and 96% of the population has AA or Aa.

  9. C. Solving Problems • 3. The Hardy-Weinberg equation shows the frequency of the dominant allele (A) as “p” and frequency of the recessive allele (a) as “q”. The sum must equal 100%. • P + q = 1

  10. C. Solving Problems • 4. Recall from punnett squares, crosses that involve these alleles have 3 possible genotypes: AA, Aa, aa

  11. C. Solving Problems • 5. Those genotypes are expressed by this equation: p2 + 2pq + q2=1 • p2= frequency of AA homozygotes • 2pq=frequency of Aaheterozygotes • q2= frequency of aahomozygotes • 1= sum of allfrequencies of all genotypes (100%)

  12. D. Practice!! • 1. In a given generation, we find that p=0.8 and q=0.2. How can you figure out the relative frequencies of AA, Aa, and aa?

  13. E. Conclusion • 1. As long as the Hardy-Weinberg conditions hold, neither the frequency of the genotypes nor the frequency of the alleles (p and q) will change from generation to generation.

  14. Partner Problems! • 1. In a given generation, we find that p=0.5 and q=0.5. How can you figure out the relative frequencies of AA, Aa, and aa. • 2. In a given generation, we find that p=0.1 and q=0.9. How can you figure out the relative frequencies of AA, Aa, and aa

  15. Challenge Problem • 1. In a population of dragons, the allele for blue scales is dominant over the allele for red scales. After surveying one population, there are 75% of dragons with blue scales and 25% of dragons with red scales. What is the frequency of the following genotypes: • Homozygous Dominant • Homozygous Recessive • Heterozygous

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