Answer to Question #205681 in Genetics for sadasz

Question

Variable expressivity, in contrast to penetrance, occurs when an individual has the allele in question and is clinically affected

Answer 1

Complete” penetrance means the gene or genes for a trait are expressed in all the population who have the genes.Expressivity on the other hand refers to variation in phenotypic expression when an allele is penetrant. Back to the polydactyly example, an extra digit may occur on one or more appendages.