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What causes Klinefelter syndrome (KS)?

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The extra chromosome results from a random error that occurs when a sperm or egg is formed; this error causes an extra X cell to be included each time the cell divides to form new cells. In very rare cases, more than one extra X or an extra Y is included.


Last Updated Date: 11/30/2012
Last Reviewed Date: 11/30/2012
Vision National Institutes of Health Home BOND National Institues of Health Home Home Storz Lab: Section on Environmental Gene Regulation Home Machner Lab: Unit on Microbial Pathogenesis Home Division of Intramural Population Health Research Home Bonifacino Lab: Section on Intracellular Protein Trafficking Home Lilly Lab: Section on Gamete Development Home Lippincott-Schwartz Lab: Section on Organelle Biology