A Trait Is Caused by a Rare Dominant Autosomal Allele

Multiple Choice

A trait is caused by a rare dominant autosomal allele with full penetrance. Practically all individuals with the trait are heterozygous and result from matings between affected and normal individuals. What would be the expected concordance values for monozygotic and dizygotic twins?

A) 100% for both types of twins
B) 100% for monozygotic twins and 90% for dizygotic twins
C) about 90% for both types of twins
D) 100% for monozygotic twins and 50% for dizygotic twins
E) 75% for monozygotic twins and 25% for dizygotic twins