Which of the following persons is virtually certain to develop Huntington disease (HD)?
A) a person who has 27-35 copies of the repeated sequence
B) a person who has 36-40 copies of the repeated sequence
C) a person who has over 40 copies of the repeated sequence
D) a person who has 10-26 copies of the HD gene
E) someone exposed to the infectious bacteria causing Huntington disease

Question

Quizplus · Accepted Answer

HD is caused by a genetic mutation involving the HTT gene located on chromosome 4. The mutation is an expansion of the CAG trinucleotide repeat sequence in this gene, and the number of repeats determines whether a person is at risk for developing the disease. Individuals with over 40 CAG repeats are virtually certain to develop HD, while those with 36-40 repeats have a high probability of developing it. Those with 27-35 repeats may develop symptoms later in life, while those with fewer than 27 repeats are considered normal. Exposure to infective bacteria does not cause HD.

Which of the Following Persons Is Virtually Certain to Develop