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NBME 22 Answers

nbme22/Block 4/Question#40

A 5-year-old boy with mental retardation is grossly ...

Maternal origin of both chromosomes 15

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Prader Willi = Paternal deletion (partial or full). Noted for imprinting. Cousin to Angelmann (opposite deletion).

FA 2017: 25% of cases due to maternal uniparental disomy (two maternally imprinted genes are received; no paternal gene received).

drjungly  Physeo video explain this very clearly, +  




Fact: 75% are due to a deletion in the long arm of the chromosome 15.

Input: This question tricked me up because when I saw a deletion in the chr15 as an option I though "I got it" but actually I did not because it is not in the short arm is in the long arm.