What is Down syndrome?

There is a nucleus in every cell in the human body where genetic material is stored in genes.  Genes carry the codes responsible for all of our inherited traits and are grouped along with rod-like structures called chromosomes.  Typically, the nucleus of each cell contains 23 pairs of chromosomes, half of which are inherited from each parent. Down syndrome occurs when an individual has a full or partial extra copy of chromosome 21.

This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome. A few of the common physical traits of Down syndrome are low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm – although each person with Down syndrome is a unique individual and may possess these characteristics to different degrees, or not at all.

There are three types of Down syndrome Trisomy 21 (nondisjunction) accounts for 95% of cases, Translocation accounts for about 4%, and Mosaicism accounts for about 1%.

The cause of the extra full or partial chromosome is still unknown. Maternal age is the only factor that has been linked to an increased chance of having a baby with Down syndrome resulting from nondisjunction or mosaicism. There is no definitive scientific research that indicates that Down syndrome is caused by environmental factors or the parents’ activities before or during pregnancy.   The additional partial or full copy of the 21st chromosome causes Down syndrome to originate from either the father or the mother. Approximately 5% of the cases have been traced to the father