Principles of Inheritance and Variation Question 191
191. Mental retardation in man associated with sex chromosomal abnormality is usually due to
(a) increase in $X$ complement
(b) moderate increase in $Y$ complement
(c) large increase in $Y$ complement
(d) reduction in $X$ complement
Show Answer
Answer : a
Hints & Solution
(a) Mental retardness is usually found when there are more than two $X$ chromosomes. About $1 %$ of all mentally defective men have one or more extra X chromosomes.
