CGC Population Genetics & Epidemiology 1 — Questions and Answers
Question 1: Hardy-Weinberg equilibrium requires which of the following conditions?
- Small population size with genetic drift
- Random mating, no mutation, no migration, no selection, and large population size (Correct answer)
- Positive selection for advantageous alleles
- High rates of consanguinity
Correct answer: Random mating, no mutation, no migration, no selection, and large population size
Hardy-Weinberg equilibrium is maintained in large, randomly mating populations free of mutation, migration, and selection pressure.
Question 2: In a population where the frequency of a recessive allele (q) is 0.1, the expected carrier frequency under Hardy-Weinberg equilibrium is:
- 0.01 (1%)
- 0.18 (18%) (Correct answer)
- 0.02 (2%)
- 0.81 (81%)
Correct answer: 0.18 (18%)
Carrier frequency = 2pq = 2 × 0.9 × 0.1 = 0.18, meaning 18% of the population are heterozygous carriers.
Question 3: The founder effect in genetics refers to:
- The discovery of a new genetic variant by a researcher
- Reduced genetic diversity in a population descended from a small founding group (Correct answer)
- The increased genetic diversity seen in hybrid populations
- The founding of a genetic counseling clinic
Correct answer: Reduced genetic diversity in a population descended from a small founding group
The founder effect occurs when a small isolated group establishes a new population, leading to high frequencies of alleles present in the original founders.
Question 4: Genetic drift is MOST significant in:
- Large, outbred populations
- Small, isolated populations (Correct answer)
- Populations with high mutation rates
- Populations experiencing strong positive selection
Correct answer: Small, isolated populations
Genetic drift causes random fluctuation in allele frequencies that is most pronounced in small populations where chance events have a larger proportional impact.
Question 5: Which term describes the increased frequency of a condition in offspring of consanguineous couples compared with the general population?
- Pleiotropy
- Autozygosity (Correct answer)
- Penetrance
- Heterozygote advantage
Correct answer: Autozygosity
Autozygosity refers to inheriting identical-by-descent alleles from a common ancestor, which increases the risk of homozygosity for recessive pathogenic variants in consanguineous offspring.
Question 6: The concept of 'heterozygote advantage' explains the persistence of cystic fibrosis alleles in European populations through the hypothesis that:
- CF carriers have a higher reproductive rate by chance
- CF carriers may have had increased resistance to certain infectious diseases such as cholera (Correct answer)
- The CF allele mutates frequently from normal alleles
- Natural selection has no effect on CF allele frequencies
Correct answer: CF carriers may have had increased resistance to certain infectious diseases such as cholera
One hypothesis for the persistence of CFTR variants is that carriers may have had a survival advantage against chloride-depleting infections like cholera.
CGC Population Genetics & Epidemiology 1
Hardy-Weinberg equilibrium requires which of the following conditions?