Molecular Biology/Genetics USMLE Step 1 Practice Question
A 45-year-old male is diagnosed with cancer of the proximal portion of the colon. His father died of colon cancer at the age of 52. He has 3 siblings. His 55-year-old brother has not been diagnosed with cancer, but his 57-year-old sister has an endometrial carcinoma, and his other sister died of ovarian cancer. A diagnosis of hereditary nonpolyposis colorectal cancer (HNPCC) is made. Which of the following types of mutations most likely occurred in this family?
Answer choices
- ALoss of the retinoblastoma (RB) tumor suppressor gene
- BA mutation causing defects in the mismatch repair system
- CA point mutation in the gene coding for an excision exonuclease
- DA mutation causing defects in the mismatch repair systemCorrect answer
- EA reciprocal translocation between chromosomes 8 and 14, associated with the Epstein-Barr virus
- FAPC mutation causing FAP
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