What is Down syndrome? Everyone has heard of Down syndrome but does anyone really know what it is and the causes of Down syndrome. The characteristics of a person with Down syndrome can be recognized by virtually everyone. A British doctor, John Langdon Down, discovered the genetic condition caused by extra genes in the 21st chromosome in 1866. Dr. Lejeune did not document the actual chromosomal nature of Down syndrome until 1959. (Thompson, McInnes, & Willard, 1991).
About 1 in 1,000 live births in the United States are born with Down syndrome. Ethnicity, socioeconomic status, culture, and geographic region have no barring on who gets Down syndrome. Some characteristics of a child with Down syndrome have a certain degree of mental retardation, or cognitive disability and other developmental delays. Other characteristics are folds over the eyes, flattened bridge of the nose, decreased muscle tone, and often are over weight. (Thompson, McInnes, & Willard, 1991) Now the cause of the extra 21st chromosome in the gene is unknown, but we do know that extra proteins have something to do with it. The age of the mother has a great effect on weather the child has down syndrome. The older the woman the greater the chances are of having a baby with Down syndrome. Odds of having a child with Down syndrome at age 35 are about 1 in every 350. Under the age of 25 the odds are about 1 in every 1400. And at the age of 40 the odds are about 1 in every 100. (Thompson, McInnes, & Willard, 1991) Now there are three different types of Down syndrome called Trisomy 21, Translocation, and Mosaicism. Trisomy 21 is the most common type of Down syndrome. 95% of people with Down syndrome have Trisomy 21. In Trisomy 21 there are 3 instead of 2 number 21 chromosomes. Usually during the formation in Trisomy 21 the 21st chromosomes does not split and a double dose goes to the egg. (Cooley & Graham, 1991) Translocation is the second kind of Down syndrome.