Principles of Inheritance and Variation Question 209
209. Down’s syndrome is due to
[1992]
(a) crossing over
(b) linkage
(c) sex-linked inheritance
(d) nondisjunction of chromosomes
Show Answer
Answer : d
Hints & Solution
(d) Down’s syndrome is due to nondisjunction of chromosomes. Non-disjunction means absence of separation of two homologous $X$ chromosomes during anaphase-I of meiosis. Both $X$ chromosomes go together to same pole. Other pole will receive no $X$ chromosome.
