Maternal disomy of chromosome 15 is seen in ?

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.