Medical MCQ - A 3-year-old boy has had progressive developmental delay, ataxia, seizures, and inappropriate laughter since infancy. The child has a normal karyotype of 46, XY, but DNA analysis shows that he has inherited both of his number 15 chromosomes from his father. These findings are most likely to be indicative of which of the following genetic mechanisms?

A 3-year-old boy has had progressive developmental delay, ataxia, seizures, and inappropriate laughter since infancy. The child has a normal karyotype of 46, XY, but DNA analysis shows that he has inherited both of his number 15 chromosomes from his father. These findings are most likely to be indicative of which of the following genetic mechanisms?

Genomic imprinting

Maternal inheritance pattern

Mutation of mitochondrial DNA

Trinucleotide repeat expansion

Question Category:

Pathology

Correct Answer:

Genomic imprinting

Description:

This child has features of Angelman syndrome, and the DNA analysis shows uniparental disomy. The Angelman gene encoded on chromosome 15 is subject to genomic imprinting. It is silenced on the paternal chromosome 15, but is active on the maternal chromosome 15. If the child lacks maternal chromosome 15, there is no active Angelman gene in the somatic cells. This gives rise to the abnormalities typical of this disorder. The same effect occurs when there is a deletion of the Angelman gene from the maternal chromosome 15. The other listed options do not occur in uniparental disomy.

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