What Can Be Inferred About a Genetic Disorder That,when It

Multiple Choice

What can be inferred about a genetic disorder that,when it occurs in monozygotic twins,affects one twin 80% of the time and affects both twins only 20% of the time?

A) Expression of homologous genes is influenced by the gender of the parent who contributed them.
B) Nongenetic factors can influence expression of identical alleles.
C) The mutation occurred in a somatic cell rather than a germ cell.
D) Mutation repair is incompletely penetrant.