d. Expressivity refers to the range of expression of a given phenotype.
e. Penetrance refers to the percentage of individuals that expresses the mutant phenotype.
Explanation:
Penetrance is the probability of a gene being expressed. Sometimes, phenotype is not observed even when the dominant allele is present. It is a result of various genetic and environmental factors coming together.This phenomenon is called as incomplete or reduced penetrance. For example: polydactyly trait is produced by a dominant allele but its penetrance is low in general population hence few people show this trait.
Expressivity is the variation in phenotypic expression when an allele is penetrant. Same genetic combination for a trait can have different expressivity in the same population. This phenomenon is also a result of genetic and environmental factors acting together. For example: people who do end up showing polydactyly trait may show it to different degrees. Some might have one extra finger, some might have two. Some might have a stub, some might have a full grown finger.
