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

Options

A. reduction in X-complement
B. increase in X-complement
C. moderate increase in Y-complement
D. large increase in Y-complement

Answer

B

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)