HardyWeinberg and Genetic Equilibrium Page 400 A HardyWeinberg

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 • 2. When allele frequencies remain constant, that is called genetic equilibrium (no evolution).

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

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

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

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

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.

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

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

C. Solving Problems • 5. Those genotypes are expressed by this equation: p 2 + 2 pq + q 2=1 – p 2= frequency of AA homozygotes – 2 pq=frequency of Aa heterozygotes – q 2= frequency of aa homozygotes – 1= sum of allfrequencies of all genotypes (100%)

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?

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.

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

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