What is the expected outcome of any pregnancy or child produced by two parents who are each heterozygous for the Huntington disease allele?
A)The couple cannot produce children who are unaffected.
B)Homozygous offspring will express the disease in childhood instead of as an adult.
C)A child who is homozygous for the mutated alleles is not likely to transmit the disorder to his or her children.
D)Because of the possibility of incomplete or low penetrance, an unaffected offspring could have an affected child.

Question

Quizplus · Accepted Answer

Huntington disease is an autosomal-dominant disorder with very high penetrance. A heterozygous person always develops the disorder, but the age of onset and the rate of disease progression can vary. This disorder does not show homozygous genotypes because homozygosity appears lethal, with loss at the embryonic or fetal pregnancy stages or within the first 12 months after birth. Thus, even if a child is born who is homozygous for the Huntington disease mutation, he or she will not live long enough to transmit the allele.

What Is the Expected Outcome of Any Pregnancy or Child