<prompt> Maternal disomy of chromosome 15 is seen in ?Prader - Willi syndromeKlinefelters syndromeAngelman syndromeTurners syndrome  <response>: Ans. is a i.e., Prader-willi syndrome In Prader- Willi syndrome, about 60 of cases have maternal uniparental disomy maternal UPD- missing the paternal chromosome 15. o Uniparental disomy UPD occurs when both chromosomes of a pair of chromosomes in a person with a normal number of chromosomes have been inherited from only one parent. o It can be of maternal maternal UPD or paternal origin paternal UPD. o For example, Russell- Silver syndrome UPD maternal Chromosome 7 Prader- Willi syndrome, UPD maternal chromosomel5 in 60 cases. Angelman syndrome UPD paternal chromosome 15 in 5. o It can be : Uniparental isodisomy Uniparental heterodisomy o Uniparental isodisomy paicularly impoant when the parent is a carrier of an autosoma recessive disorder. The child will develop an autosomal recessive disorder even though one parent is a carrier of that recessive disorder. o The autosomal recessive disorders spinal muscular atrophy, cystic fibrosis, cailage- hair hypoplasia, and f, - thalassemias, and Bloom syndrome have occurred because of uniparental disomy. 