Question

(a) Identify the syndrome from the diagram, and write the genotype.
(b) It occurs in both sexes (male and female) ? Write the reason.

Answer 1

(a) Down's syndrome is mainly caused due to an extra copy of chromosome 21. The extra copy is formed due to non-disjunction of chromosomes during meiosis. In this case, as the two chromosomes of the child has the same allele as the mother so it can be concluded that the non-disjunction has taken place during maternal meiosis with duplication of maternal allele. The genotype of this individual is 45A + XX/XY.

(b) This is an autosomal disorder and can occur in the males as well as in the females.