Klinefelterís Syndrome occurs as the result of an error during the formation of an egg or a sperm that results in a person having a XXY combination or 47 chromosomes instead of the normal 46.
A normal person has a total of 46 chromosomes in each cell. Two of these chromosomes are called X and Y and these are responsible for the sex of a person. Females have two X chromosomes Ė 46, XX, and males have one X and one Y chromosome Ė46, XY.
Klinefelterís Syndrome is caused by the presence of an additional X chromosome. This error usually occurs when the chromosomes are distributed during the division of the egg or the sperm. In more than half of the cases, the extra X chromosome is contributed by the father. Very little is known about the role of the motherís age in bringing about this condition.