Molecular Biology/Genetics USMLE Step 1 Practice Question
A 45-year-old male with a confirmed diagnosis of hemochromatosis tests negative for the 2 most common mutations in the HFE gene known to cause this disease. The patient and several family members, including an affected brother and uncle, are tested for 5 single nucleotide polymorphisms (SNPs) closely linked to the HFE gene on chromosome 6. No linkage is found in this family to any of these markers. What is the most likely explanation for these results?
Answer choices
- AIncomplete penetrance
- BHeteroplasmy
- CLocus heterogeneityCorrect answer
- DA rare HFE allele
- ERecombination between the SNPs and the HFE gene
- FMitochondrial inheritance of hemochromatosis
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.