For an autosomal dominant disease, if two affected parents have a child, what is most likely the risk of passing on the disorder?
A) 0
B) 25%
C) 50%
D) 75%
E) 100%

Question

Quizplus · Accepted Answer

In an autosomal dominant disease, each affected parent has at least one dominant allele for the disease. When both parents are affected, their genotypes could be either heterozygous (Aa) or homozygous dominant (AA). The possible offspring genotypes are AA (affected), Aa (affected), and aa (unaffected). The only way for the child to not inherit the disease is if both parents pass on the recessive allele (a), which occurs in 1 out of 4 scenarios if both parents are heterozygous. Therefore, there is a 75% chance (3 out of 4 scenarios) that the child will inherit the disease.

For an Autosomal Dominant Disease, If Two Affected Parents Have