Sex chromosomal Aberrations | Anthropology Optional for UPSC PDF Download

Introduction

• Non disjunction produces gametes with extra sex chromosomes; one would also expect trisomy of the sex chromosomes if the gametes containing an extra sex chromosome took part in fertilization. Conditions resulting from trisomy of the sex chromosome's fact occur even more frequently then the Turner's syndrome.
• If a sperm from nondisjunction were to fertilize a normal X bearing one, and XX ovum rising from  nondisjunction in oogenesis were to be fertilized, by a normal Y bearing sperm, the zygotes in each case would be XXY.
• This imbalances in the number of sex chromosomes leads to a series of abnormalities known collectively as Kleinefelter's Syndrome.
• An extra X chromosome in addition to the usual male XY chromosome complement (47, XXY) has been associated with the abnormal male syndrome described by H.F. Kleinefelter. It is estimated to occur in 1 per 500 live birth, Individuals with this syndrome are phenotypically males but with some-tendency toward femaleness, particularly in secondary sex characteristics.
• Such features as enlarged breasts, underdeveloped body hair, small testes, and small prostrate glands are a part to the syndrome. Presumably, the XXY constitution originates either by fertilization of an exceptional XX egg by a Y sperm or of an X egg by an exceptional XY sperm. Studios of Kleinefelter's  syndrome and Turner's syndrome indicate that the Y chromosome in human beings determines male sex.
• The most common karyotype for Kleinefelter's syndrome is 47,XXY, but the symptoms of the syndrome will usually occur whenever more than one X chromosome is present along with a Y chromosome. More complex karyotypes associated with the Kleinefelter's syndrome include XXYY, XXXY, XXXYY, XXXXY, XXXXYY and XXXXXY. Mental retardation is usualy. found when there are more than .two X chromosomes.. Thus this syndrome brings about both physical and reproductive anomalies.

Conclusion

Kleinefelter's Syndrome is a genetic condition that occurs due to an imbalance in the number of sex chromosomes, specifically the presence of an extra X chromosome in addition to the usual male XY chromosomes. This can result from nondisjunction in the formation of gametes, leading to the formation of XXY zygotes. Individuals with this syndrome exhibit a combination of male and female secondary sex characteristics, such as enlarged breasts, underdeveloped body hair, and small testes. The most common karyotype for Kleinefelter's Syndrome is 47,XXY, but other complex karyotypes also exist, with mental retardation typically associated with more than two X chromosomes. Overall, Kleinefelter's Syndrome results in various physical and reproductive anomalies in affected individuals.