Molecular Biology/Genetics USMLE Step 1 Practice Question
A 7-year-old boy presents with declining school performance and behavioral difficulties. Vital signs are normal (BP 110/68, HR 82, RR 20, Temp 37°C). Examination reveals a long narrow face, large everted ears, hyperextensible fingers, and macroorchidism. His maternal uncle had an identical phenotype. Serum creatinine and liver function tests are normal. IQ testing shows mild intellectual disability. He denies seizures. Expansion of which of the following nucleotide repeats is the most likely cause?
Answer choices
- ACTG
- BGAA
- CATTCT
- DCGGCorrect answer
- ECAG
- FGCC
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