Down Syndrome Awareness Month

October is DS Awareness Month, and so in honor I will write some posts about DS generally, and specifically about Justin.

The first thing to know is that DS is a genetic disorder. There are 3 types of DS: nondisjunction, translocation, and mosaic.

By far the most common (95%) is nondisjunction, which is what Justin has. Nondisjunction means that there is an extra copy of the 21st chromosome, and it is attached to the other 2 copies of the same chromosome. This happens prior to conception, when either the egg or sperm is produced with an extra copy of the 21st chromosome, thus when it joins, there results in 3 copies of the chromosome.

Translocation occurs when the long arm of the 21st chromosome attaches either to itself, or typically to chromosome 14. This is the one type that can result in a person being a carrier, and not actually have DS. So this is the one type that is familial, and it is just as likely from the mother as the father. This occurs in about 2-3% of DS cases.

Mosaicism is the most rare form, found in about 1-2% of cases. Mosaic DS results during the cell division process. As the cells are dividing, an extra 21st chromosome attaches to one part of the cell as it divides, causing part of the cells to have an extra 21st chromosome, and the others to have the correct configuration.

The type of DS doesn't appear to have any affect on cognitive ability or health issues.