Mendelian Disorders

Klinefelter's syndrome (Klinefelter, 1942) is due to trisomy of sex chromosome. It is formed by the union of an abnormal XX egg and a normal Y sperm or normal X egg and abnormal XY sperm. The individual has 47 chromosomes (44 + XXY). Such persons are sterile males (called feminised male) with undeveloped testes, mental retardation, female like sparse body hair, and knock knees, long limbs and with some female characteristics such as feminine pitched voice and enlarged breasts (gynaecomastia).