DOWN SYNDROME

DOWN SYNDROME

:is a chromosomal condition caused when abnormal cell division results in extra genetic material from chromosome 21.

 

causes intellectual disability (developmental delays), Flattened facial features, Protruding tongue, small stature, an upward slant to the eyes, single deep crease across the center of the palm and weak muscle tone in infancy.

One in every 691 babies in the United States is born with Down syndrome. Approximately 400,000 Americans have Down syndrome and about 6,000 babies with Down syndrome are born in the United States each year.

There are three types of Down syndrome:  trisomy 21 (nondisjunction), translocation and mosaicism.                             

About 95% of cases Down syndrome are usually caused by nondisjunction that is called trisomy 21.   Nondisjunction results in abnormal cell division during the development of the sperm cell or the egg cell with three copies of chromosome 21 instead of the usual two. 

Mosaicism occurs when nondisjunction of chromosome 21 takes place in one but not all cells. It is caused by abnormal cell division after fertilization. Children have some cells with an extra copy of chromosome 21.  Mosaicism is rare and accounts for about 1% of all cases of Down syndrome.

About 4% of all cases of Down syndrome are translocation.  In translocation, part of chromosome 21 becomes attaches to another chromosome, typically chromosome 14.  These children have the usual two copies of chromosome 21 and total number of chromosomes in the cells remains 46 but an extra part of chromosome 21 causes the characteristics of Down syndrome. 

Risk factors: advancing maternal age, having had one child with Down syndrome, and being carriers of the genetic translocation for Down syndrome.

I have one cousin that has Down Syndrome because of  his mother maternal age. I think that this kind of children needs really good educational support. My cousin knew the capital city of most of the countries in the world at age 4. His mom and sister really support him and speak with him all the time. it is really good for them to have as much as communication with people. they can not grow up like other children but at least they can be good in their ways. 

http://geneticdisordersp7.wikispaces.com/Down+Syndrome

http://comd281-summerwiki.wikispaces.com/Group+5++Down+Syndrome

http://www.chw.org/medical-care/genetics-and-genomics-program/medical-genetics/chromosome-abnormalities/types-of-chromosome-abnormalities/structural-abnormalities/translocations/

http://ghr.nlm.nih.gov/condition/down-syndrome