Question

Mental retardation in man associated with sex chromosomal abnormality is usually due to

• A. Increase in size of X-chromosome
• B. Increase in size of Y-chromosome
• C. Increase in number of Y-chromosome
• D. Increase in number of X-chromosome

Answer 1

The correct option is A Increase in size of X-chromosome

Mental retardation in a man is associated with X linked recessive inheritance. In the case of X linked disorders, males are most heavily affected compared to females. Females with one affected X chromosome and one normal X chromosome tend to have milder symptoms. Mental retardation in a man is associated with an increase in the size of the X chromosome.

So the correct answer is A