population genetics

Question 1

hardy winberg equation

Answer 1

(P+Q)²=P²+2PQ+Q²

CCR5/CCR5 = p² = (0.906)² = 0.820 CCR5/ ∆CCR5 = 2pq = 2(0.906) (0.094) = 0.17 ∆CCR5/∆CCR5 = q² = (0.094)2 = 0.009

Question 2

assuptions for hardy winberg

Answer 2

• pop size is large and mating is random
• alle frequencies remain constant over time becasue
  
  • there is no appreciable rate of mutation
  • there is no selection against any particular genotype
  • there is no inflo or outflow of the population

Question 3

exceptions to random mating

Answer 3

stratification - same ethnic background

assortive mating - simalar abilities

consanguinity- mating with in blood relative

Question 4

Assortative Mating

Answer 4

The choice of a mate because the mate possesses a particular trait.

The result is the increase in the proportion of homozygotes at the expense heterozygotes in the population

The genotype of the mate at the disease locus is not determined by allele frequencies in the population, and hence HW equilibrium does not apply.

• Non-allelic mutations can result in the same phenotype: two deaf partners can have normal offspring, because of locus heterogeneity.

Question 5

Stratification

Answer 5

The net result of stratification is that when viewed as a whole, there will be a greater than expected homozygotes and fewer than expected heterozygotes. (since the subgroups do not interbreed, the probability of two carrier matings is greater than expected from a truly large population with random mating)

Question 6

Exceptions to Constant Allele Frequency

Answer 6

in contrast, changes in allele frequency are usually slower, and occur in small increments and cause less deviation of the HW equilibrium

• Examples are: – Selection – Mutation – Migration

Question 7

Assuming that an X-linked recessive disorder occurs in 1 in 200 male births, what is the frequency of affected females?

Answer 7

0.000025

Question 8

Which of the following terms describes the small, random effects that cause changes to allele frequencies in small populations?

Genetic drift

Genetic isolation

Population stratification

Natural selection

Assortative mating

Answer 8

Genetic drift

Question 9

Ned and Stacey are the parents of Mark, a child affected with a fully penetrant, autosomal recessive disorder that is easily diagnosed at birth, and occurs in the population with an incidence of 1/3600. Neither Ned nor Stacey has this disorder themselves. Their next child, Tony, is born without any apparent signs of the disease. Tony grows up and marries Maria, a woman with no known family history of the disorder. The chance that Tony and Maria’s first child will be affected with the same disorder that affects Mark is closest to which of the following numbers?

Answer 9

1/180

Question 10

If an autosomal recessive disorder occurs in the US Ashkenasic Jewish population with an incidence of approximately 1/6400, the chance that two people, randomly drawn from this population will both be carriers for the mutation is closest to which of the following?

Answer 10

1/1600

Question 11

In a population in Hardy-Weinberg equilibrium, the frequency of a recessive allele will ____ over time

Answer 11

remain the same

Question 12

Assuming Hardy-Weinberg equilibrium, what percentage of individuals are heterozygous if p = 0.6?

Answer 12

48