An individual with a father who developed Huntington's disease and a mother who was never at risk for it will develop the disease unless she
A) inherited a normal allele from her mother and none from her father.
B) inherited only the dominant allele from her father and none from her mother.
C) experienced significantly different environmental conditions from her father.
D) experienced a significant genetic mutation at the time of fertilization.

Question

Quizplus · Accepted Answer

Huntington's disease is an autosomal dominant disorder, which means that a child has a 50% chance of inheriting the mutant allele from their affected parent. Since the individual's father had Huntington's disease, he must have had at least one copy of the mutant allele. However, not all of his children will necessarily develop the disease because they may inherit a normal allele from their unaffected parent. In this case, the individual's mother is not at risk for the disease, so she must have two copies of the normal allele. Therefore, if the individual inherits a normal allele from her mother and none from her father, she will not develop the disease.

An Individual with a Father Who Developed Huntington's Disease and a Mother