Question

An abnormal human male phenotype involving an extra X-chromosome (XXY) is a case of

(a) Edward’s syndrome

(b) Klinefelter’s syndrome

(c) intersex

(d) Down’s syndrome.

Answer 1

The correct answer is option (b) Klinefelter syndrome; it describes a group of chromosomal disorder in which there is at least one extra X chromosome to a normal male karyotype, 46, XY. XXY aneuploidy is the most common disorder of sex chromosomes in humans. Males inherit one or more extra X chromosomes--their genotype is XXY or more rarely XXXY or XY/XXY mosaic.  In severe cases, they have relatively high-pitched voices, asexual to feminine body contours as well as breast enlargement, and comparatively little facial and body hair. They are sterile or nearly so, and their testes and prostate gland are small. As a result, they produce relatively small amounts of testosterone. The feminizing effects of this hormonal imbalance can be significantly diminished if klinefelter syndrome boys are regularly given testosterone from the age of puberty.