A trait is caused by a rare recessive autosomal allele with full penetrance. Practically all individuals with the trait result from matings between 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 50% for dizygotic twins
C) about 50% for both types of twins
D) 100% for monozygotic twins and 75% for dizygotic twins
E) 100% for monozygotic twins and 25% for dizygotic twins

Question

Quizplus · Accepted Answer

Monozygotic twins share 100% of their genes, so if one has the trait, the other will too. Dizygotic twins share about 50% of their genes, so the concordance for a recessive trait would be about 25%.

A Trait Is Caused by a Rare Recessive Autosomal Allele