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, also called testicular dysgenesis, is the phenotype of the 47,XXY genotype and is characterized by male hypogonadism and infertility. is probably the most common chromosomal variation found in humans. In random surveys, it is found to appear about once in every ....

Middle of Essay
.... chromosome causes the distinctive make-up of these boys. All men have one X chromosome and one Y chromosome, but sometimes a variation will result in a male with an extra X. This is and is often written as 47,XXY. There are other, less common variations such as 48,XXYY; 48,XXXY; 49,XXXXY; and XY/XXY mosaic. All of these are considered variants. The major effect of the extra X chromosome in boys with seems to be the function of the testes. The testes produce the major male sex hormone testosterone and the amount of this hormone may be decreased in boys with . When these boys reach 10-12 years of age, it is helpful to measure their blood hormone l ....