Klinefelter syndrome, 47, XXY, or XXY syndrome is a genetic disorder where people have an extra number of X chromosomes. People who have Klinefelter's Syndrome are often called "XXY Males", or "47, XXY Males".
In other organismsEdit
Other males can have Klinefelter's Syndrome as well as humans. The mouse is one example. Tortoiseshell or calico markings on male cats are an indicator of a similar syndrome. These cats are considered to be the model organism for Klinefelter syndrome, because the gene for a cat's tabby coat markings is found on the X chromosome. 
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