Question

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

(a) reduction in X-complement 

(b) increase in X-complement 

(c) moderate increase in Y-complement 

(d) large increase in Y-complement 

Answer 1

Correct option (b) increase in X-complement 

Explanation

Sterile males with undeveloped. testes, mental retardation, etc. are due to increase in their X-complement which takes place in a disorder called Klinefelter's syndrome. These are formed by union of an XX egg and a normal y sperm or normal X egg and abnormal XY sperm. The individual thus has 47 chromosomes (44 + XXY).