Sarah's mother has Huntington's disease,an illness that results from a dominant gene,but her father does not.What is the likelihood that Sarah herself will develop the disease?

Question

Quizplus · Accepted Answer

Since Huntington's disease is caused by a dominant gene, if Sarah's mother has the disease, she must have at least one copy of the gene for it. Sarah has a 50% chance of inheriting that gene from her mother, and a 50% chance of inheriting a healthy allele from her father. Therefore, Sarah has a 50% chance of developing Huntington's disease. Option A is not correct because even though Sarah's father does not have the disease, he could still be a carrier. Option C is not correct because a person with only one copy of the gene for Huntington's disease can still develop the disease. Option D is not correct because the disease is caused by a dominant gene, so inheriting a healthy allele from her father does not affect her chance of developing the disease if she inherits a copy of the gene from her mother.

Sarah's Mother Has Huntington's Disease,an Illness That Results from a Dominant