In an autosomal Recessive (AR) disorder, one parent is normal and the other is carrier and the child is also affected. What is the reason?
Correct Answer: Uniparental disomy
Description: If one parent is normal for an autosomal recessive disorder and the other is carrier - No child should be affected. But there is exception to this rule, i.e. uniparental disomy (UPD), when a person receives 2 copies of a chromosome, from one parent and no copies from the other parent. Ex: In Prader-Willi syndrome- maternal UPD of chromosome 15 (missing the paternal chromosome 15). In Angelman syndrome- paternal UPD of chromosome 15 (missing the maternal chromosome 15).
Category:
Pediatrics
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