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XYY syndrome
Background
XYY syndrome is a chromosomal condition which occurs only in males and is found with a frequency of 1 in 1,000. A chromosome is a rod-like structure present in the nucleus of all body cells, with the exception of the red blood cells. Chromosomes store genetic information. Normally humans have 23 pairs of chromosomes, 46 chromosomes in total. The twenty-third pair, otherwise referred to as the sex chromosomes, store genetic information which determine our sex. A female has a XX pair and a male has a XY pair of chromosomes.
A male affected by XYY syndrome has an additional Y chromosome as well as the usual XY pair of chromosomes resulting in the formation of XYY. Sometimes the additional Y chromosome is present in only some of the cells of the body, but not all. This is referred to as a mosaic form of XYY syndrome. The extent to which such an individual is affected by XYY syndrome depends upon the proportion of XYY cells to XY cells throughout the body.
