The History Behind Down Syndrome Genetics By Mike Selvon

One in 1,000 American babies is born with the Down syndrome genetic condition, although it is estimated that 90% of the mothers who receive an early diagnosis choose abortion. There are many fallacies about people with Down syndrome that scare parents into making a rash decision. Most adults with Down syndrome live independently, marry, have jobs and live past their fifties nowadays.

There are many ways the genetic data of Down syndrome can be damaged or rearranged. For example, in trisomy 21, one parent has two chromosomes located at chromosome #21, rather than one, causing the child to receive two chromosomes from one parent and one from the other parent for a total of three. The Down syndrome child will then have 47 chromosomes, instead of 46. This occurs in 90% of all Down syndrome cases.

With Mosaic syndrome disorder, chromosome 21 gets damaged during cell replication, where two normal chromosomes become three in some cells. People with this disorder have some cells with 46 chromosomes and some cells with 47 and their symptoms may be less severe.

This occurs in 2% of all Down syndrome cases. The last type of Down syndrome is called Translocation and occurs when a normal chromosome breaks into two pieces and attaches to another chromosome. This occurs in 3-4% of all Down patients.

Prior to pregnancy, parents can meet with a genetic counselor to determine their risk of passing on a Down syndrome genetic code. Sometimes disorders run in the family, if more than one person has the condition. In other cases, mothers over the age of 35 may have an increased risk for having Down syndrome babies or, in rare instances, environmental factors can play a part.

Some Down syndrome research suggests that smoking while being on birth control can cause the syndrome, although it is debated in some circles. Once pregnant, a woman can go for ultrasound, non-invasive blood tests or undergo amniocentesis for a more accurate assessment.

The severity of Down syndrome varies greatly from person to person. There is not much Down syndrome genetic research on the specific differences between trisomy 21, Translocation and Mosaic syndrome, at present. However, a 1991 report suggested that children with Mosaic syndrome had a mean IQ of 12 points higher than children with typical Down syndrome.

Yet some children with typical Down syndrome still scored higher, which underscores the uniqueness of every child. The Department of Human Genetics at the Medical College of Virginia reported that children with Mosaic syndrome reached their motor milestones earlier than children with typical DS, but speech development was equally delayed in both test groups.