 | Down Syndrome is a chromosomal disorder that causes persons to be born with 47 chromosomes instead of 46, resulting in significant physical and cognitive deficits. The genetic condition affects 1 in every 691 babies (Facts, 2012). Persons with Down Syndrome have easily recognizable facial features and experience a range of developmental delays in childhood. Initial identification is usually based upon the way a child looks, and is diagnosed by a study of the chromosomes. This website will explain the physical characteristics and cognitive deficits associated with the condition, explore the complex issues involved with educating children with Down Syndrome, as well as provide information about advocacy and support groups in the United States. |
For a great summary of Down Syndrome, visit the National Association of Down Syndrome's "Facts About Down Syndrome" page. http://www.nads.org/pages_new/facts.html
Types:
There are three types of Down Syndrome, all involving abnormal cell division of chromosome 21. The most common type is Trisomy 21, with over 90 percent of the Down Syndrome cases (Mayo Clinic, 2012). In this type, cell division during sperm cell or egg cell development results in a child having three copies of chromosome 21 in every single cell of the body, instead of the typical two copies. The second type of Down Syndrome is called Mosaicism. Abnormal cell division after fertilization causes the child to have an extra copy of chromosome 21 in some of his or her cells. Translocation is the final type, and occurs when part of chromosome 21 attaches to another chromosome. It is important to note that as the mother's age increases, so does the prevalence of Down Syndrome births, as shown in the diagram below.
