Stephen J. Schueler, M.D.

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Down's Syndrome Underlying Cause

Normally, a person has 23 pairs of chromosomes. One of each pair is donated from the mother, and one from the father. Down's syndrome occurs when there is an extra 21st chromosome. The extra chromosome can come from the mother's egg or the father's sperm. However, in most cases, it comes from the mother's egg. It is unknown why the egg or sperm carries the extra chromosome. The syndrome results from the directions that the cells receive from this extra DNA.

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Last Updated: Jun 18, 2008 References
Authors: Stephen J. Schueler, MD; John H. Beckett, MD; D. Scott Gettings, MD
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PubMed Down's Syndrome References
  1. Bahado-Singh RO, Sutton-Riley J. Biochemical screening for congenital defects. Obstet Gynecol Clin North Am. 2004 Dec;31(4):857-72, xi. [15550339]
  2. Matias A, Montenegro N, Blickstein I. Down syndrome screening in multiple pregnancies. Obstet Gynecol Clin North Am. 2005 Mar;32(1):81-96, ix. [15644291]
  3. Taub JW, Ge Y. Down syndrome, drug metabolism and chromosome 21. Pediatr Blood Cancer. 2005 Jan;44(1):33-9. [15390307]
  4. Tyler C, Edman JC. Down syndrome, Turner syndrome, and Klinefelter syndrome: primary care throughout the life span. Prim Care. 2004 Sep;31(3):627-48, x-xi. [15331252]
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