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USMLE · Question #415
USMLE Question #415: Real Exam Question with Answer & Explanation
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Question
A couple has a daughter who is ataxic and has a seizure disorder. She also has a strange affect characterized by excessive laughter at inappropriate times. Cytogenetic analysis demonstrates a normal genotype with 46 chromosomes and no apparent deletions. These symptoms are most likely due to:
Options
- Aconfined placental mosaicism
- Bexpansion of a trinucleotide repeat
- Ca point mutation in an autosome
- Drandom inactivation of the X chromosome
- Euniparental disomy
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