Question

Penetrance and expressivity refer to a. the proportion who get the disease and how the disease manifests respectively b. redundant terms c. how the disease manifests and the proportion who get the disease respectively d. all of the above e. none of the above

Short answer

Answer: Penetrance is the proportion of individuals carrying a specific variant of a gene that also express an associated trait or phenotype, meaning it refers to the likelihood that a genetic trait will actually be exhibited in an individual who has a specific genotype for that trait. Expressivity, on the other hand, is the range of expression of a genotype on a phenotype or the degree to which the trait caused by a genotype is manifested in an individual. It refers to the variation in a phenotype among individuals carrying a particular genotype. Both penetrance and expressivity are essential to understand the relationship between genotypes and phenotypes in genetics.

Step-by-step solution

Understanding Penetrance

Penetrance is a term used in genetics to describe the proportion of individuals carrying a specific variant of a gene that also express an associated trait or phenotype. In other words, it refers to the likelihood that a genetic trait will actually be exhibited in an individual who has a specific genotype for that trait.

Understanding Expressivity

Expressivity is a term that describes the range of expression of a genotype on a phenotype or the degree to which the trait caused by a genotype is manifested in an individual. It refers to the variation in a phenotype among individuals carrying a particular genotype. Expressivity can be constant or variable, depending on the range of phenotypic outcomes that can result from a single genotype.

Identifying the Correct Definition

Now that we understand the definitions of penetrance and expressivity, we can easily identify the correct answer. Option (a) clearly defines the two terms: penetrance is the proportion of individuals who get the disease, and expressivity is how the disease manifests in those individuals. Therefore, the correct answer is (a).