A genetic counselor is consulted by a young man who is worried about developing Huntington’s disease, an inherited disorder caused by a dominant allele of a single gene. The young man explains that his cousin was recently diagnosed with Huntington’s disease, and the news has caused him to consider his own risk of developing the disorder.

Which of the following questions will best help the genetic counselor to evaluate the risk of the young man developing Huntington’s disease and transmitting it to his children?

Question

A genetic counselor is consulted by a young man who is worried about developing Huntington’s disease, an inherited disorder caused by a dominant allele of a single gene. The young man explains that his cousin was recently diagnosed with Huntington’s disease, and the news has caused him to consider his own risk of developing the disorder.

Which of the following questions will best help the genetic counselor to evaluate the risk of the young man developing Huntington’s disease and transmitting it to his children?

BlackTom AI · Accepted Answer

Question restatement: A genetic counselor is assessing a young man's risk of developing Huntington’s disease, an autosomal dominant disorder, given a cousin's recent diagnosis. The focus is on which question best informs his risk of manifesting the disease and transmitting it to offspring.
Option 1: 'Were you in physical contact with a person diagnosed with Huntington’s disease?' This query is not helpful for Huntington’s disease risk assessment because Huntington’s is not transmitted through casual physical contact or environmental exposure. It’s a heritable genetic condition, so contact history provides little to no predictive value.
Option 2: 'Were you and your cousin born in the same geographical area?' Being born in the same area does not influence Huntington’s disease risk. The risk depends on genetic inheritance, not on geographic or environmental clustering, unless there is a known founder effect—which this question does not establish. Thus this option does not meaningfully inform transmission or risk.
Option 3: 'Were your parents or grandparents ever diagnosed with Huntington’s disease?' This question directly addresses family history and the pattern of inheritance. Huntington’s disease is autosomal dominant, so having an affected parent or grandparent significantly changes the probability that the individual carries the pathogenic allele and could pass it to children. Knowledge of affected first- or second-degree relatives is central to risk calculation and genetic counseling.
Option 4: 'Were you ever exposed to substances that are suspected of being mutagens?' Huntington’s disease is caused by a known dominant mutation in the HTT gene, not by acquired mutagenic exposure. While mutagens can cause new mutations in some contexts, Huntington’s inheritance follows a familial pattern rather than a result of environmental mutagen exposure. Therefore, this question does not appropriately assess the individual's risk or transmission likelihood.
In summary, the most informative line of questioning centers on family history of the disease, especially in parents or grandparents, because it directly reflects the hereditary risk and potential transmission to offspring.

APBIO141-031 with labs S15 - CollegeBoard* AP Exam Prep: Multiple Choice

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