Q: A population of 788 individuals was genotyped for the CCR5 gene. 647 were CCR5/CCR5, 134 were CCR5/ΔCCR5, and 7 were ΔCCR5/ΔCCR5. What is the frequency of the ΔCCR5 allele ($$q$$)?

$$q = \frac{2 \times 7 + 134}{2 \times 788}$$

Q: If the frequency of the wild-type CCR5 allele ($$p) is 0.906 $$and the frequency of the ΔCCR5 allele ($$q) is 0.094$$, what is the expected frequency of heterozygotes in the population under Hardy-Weinberg equilibrium?

$$2pq = 2 \times 0.906 \times 0.094 = 0.170$$

Q: A recessive genetic disorder has an incidence of 1 in 10,000 in a population. What is the expected carrier frequency using Hardy-Weinberg law?

$$2pq = 2 \times (1 - \sqrt{1/10,000}) \times \sqrt{1/10,000} \approx 0.0198$$

Question 1

Which of the following best describes the concept of 'gene pool' in population genetics?

Accepted Answer

The collection of all alleles of all the genes found within a freely interbreeding population.

Question 2

In the Hardy-Weinberg equation $$p^2 + 2pq$$ + $$q^2 = 1$, what does 2pq$ represent?

Accepted Answer

The frequency of heterozygous individuals.

Question 3

A population of 788 individuals was genotyped for the CCR5 gene. 647 were CCR5/CCR5, 134 were CCR5/ΔCCR5, and 7 were ΔCCR5/ΔCCR5. What is the frequency of the ΔCCR5 allele ($$q$$)?

Accepted Answer

$$q = \frac{2 	imes 7 + 134}{2 	imes 788}$$

Question 4

Which of the following is NOT a condition required for Hardy-Weinberg equilibrium?

Accepted Answer

Small population size

Question 5

If the frequency of the wild-type CCR5 allele ($$p) is 0.906 $$and the frequency of the ΔCCR5 allele ($$q) is 0.094$$, what is the expected frequency of heterozygotes in the population under Hardy-Weinberg equilibrium?

Accepted Answer

$$2pq = 2 	imes 0.906 	imes 0.094 = 0.170$$

Question 6

Why are individuals homozygous for ΔCCR5 resistant to HIV infection?

Accepted Answer

The CCR5 receptor is nonfunctional, preventing HIV from entering cells.

Question 7

Which factor would most likely disrupt Hardy-Weinberg equilibrium in a population?

Accepted Answer

Genetic drift due to a population bottleneck

Question 8

A recessive genetic disorder has an incidence of 1 in 10,000 in a population. What is the expected carrier frequency using Hardy-Weinberg law?

Accepted Answer

$$2pq = 2 	imes (1 - \sqrt{1/10,000}) 	imes \sqrt{1/10,000} \approx 0.0198$$

Question 9

Which of the following best explains why the Hardy-Weinberg law is important in medical genetics?

Accepted Answer

It allows estimation of gene frequencies from disease prevalence data.

Question 10

Which real-world example demonstrates the effect of population genetics on disease allele frequency?

Accepted Answer

High frequency of sickle cell anemia allele in African populations due to malaria resistance.

Question 11

If a population does not meet the conditions of Hardy-Weinberg equilibrium, what is most likely to occur?

Accepted Answer

Allele and genotype frequencies will change over generations.

Question 12

Which equation correctly represents the relationship between allele and genotype frequencies in Hardy-Weinberg equilibrium?

Accepted Answer

$$p^2 + 2pq$$ + $$q^2 = 1$

Question 13

A population has the following genotype frequencies for a gene: AA = 0.81, Aa = 0.18, aa = 0.01. What are the allele frequencies for A and a?

Accepted Answer

$$p = 0.81 + 0.5 	imes 0.18 = 0.90$$, $$q = 0.01 + 0.5 	imes 0.18 = 0.10$$

Question 14

Which of the following is an example of a factor that can cause deviation from Hardy-Weinberg equilibrium?

Accepted Answer

Gene flow and migration

Question 15

In a population, the frequency of the ΔCCR5 allele ($$q) is 0.094. $$What is the expected frequency of individuals homozygous for ΔCCR5 under Hardy-Weinberg equilibrium?

Accepted Answer

$$q^2$$ = $$0.094^2 = 0.0088$

Question 16

Which statement about the CCR5 Δ32 mutation is correct?

Accepted Answer

It confers resistance to HIV infection in homozygous individuals.

Question 17

What is the main reason why the Hardy-Weinberg law can be used to estimate carrier frequencies for autosomal recessive diseases?

Accepted Answer

Because the law relates allele frequencies to genotype frequencies even when carriers are not phenotypically distinguishable.

Question 18

Which of the following is a real-world application of the Hardy-Weinberg law in genetic counseling?

Accepted Answer

Estimating the risk of producing an affected child when one parent is a carrier for a recessive disease.

Question 19

Which of the following loci is an example of a polymorphic locus with wide allelic variation in human populations?

Accepted Answer

ABO blood group

Population Genetics: Principles, Applications, and Disease Allele Frequencies

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