Question

Mental retardness in man occur due to :

• A. Loss of one X chromosome
• B. Addition of one X chromosome
• C. Slight growth in Y
• D. Overgrowth in Y

Answer 1

The correct option is A Loss of one X chromosome

A.Loss of one X chromosome -X-linked forms of mental retardation are estimated to cause 10-20% of all inherited cases of mental retardation.
B.Addition of one X chromosome- a male is born with an extra X chromosome (XXY),this is klinefilter syndrome
C & D. There is no slight or overgrowth in Y chromosome.
So correct answer is option -A .Loss of one X chromosome.