Population Genetics & Epidemiology Flashcards

Penetrance in genetics refers to:

Answer: The proportion of individuals with a given genotype who exhibit the associated phenotype

Penetrance is the proportion of individuals with a pathogenic genotype who show clinical features; incomplete penetrance means not all carriers are affected.

Variable expressivity in genetics means:

Answer: Individuals with the same pathogenic variant may show different degrees or types of clinical features

Variable expressivity describes the range in clinical severity or phenotypic features seen among individuals who share the same pathogenic variant.

Which measure of disease frequency represents the proportion of a population affected with a condition at a specific point in time?

Answer: Point prevalence

Point prevalence measures the proportion of individuals in a population who have a condition at a specific moment in time.

Locus heterogeneity refers to the situation where:

Answer: Mutations at different gene loci can all cause the same clinical phenotype

Locus heterogeneity means clinically similar conditions can result from variants in different genes, complicating genetic testing interpretation.

Allelic heterogeneity refers to:

Answer: Multiple different variants within the same gene causing the same or related phenotypes

Allelic heterogeneity describes the existence of multiple distinct pathogenic variants within the same gene that all produce the same or similar phenotype.

A genetic counselor explains that a condition has a population prevalence of 1 in 10,000. Using Hardy-Weinberg, the carrier frequency is approximately:

Answer: 1 in 50

For q² = 1/10,000, q = 1/100; carrier frequency 2pq ≈ 2q = 1/50, since p ≈ 1 for rare recessive conditions.