Trisomy 21 (Nondisjuncion), Mosaicism and Translocation. Coldon has Trisomy 21.
Trisomy 21 occurs when each cell in the body has three separate copies of the 21st chromosome, instead of the typical two copies. Trisomy 21 affects about 95% of people with Down syndrome. You may have seen 321 associated with different Down syndrome organizations or individuals; this is why.
Translocation occurs when an extra part or the whole extra 21st chromosome is present, but is attached “trans-located” to a different chromosome rather than being a separate 21st chromosome. Translocation affects about 3-4% of people with Down syndrome.
Mosaicism occurs when some of the cells have three copies of the 21st chromosome, but other cells have the typical two copies. Mosaicism affects about 2% of people with Down syndrome.
For more information about the three different types of Down syndrome, see http://www.ndss.org
Upon suspicion of a child having Down syndrome, a vast series of genetic testing is performed to verify if your child in fact has DS and what type it is. These tests are performed during pregnancy, at the mother’s discretion if Down syndrome is suspected and post birth. We received a post birth diagnosis and all the tests were completed while Coldon was in the NICU. Coldon was diagnosed with Trisomy 21, meaning every cell in his body has an extra copy of the 21st chromosome. (You can read about Coldon’s diagnosis under “Coldon’s Story”).
Don’t get in a hurry for these results, as the testing is extensive. The genetics team informed me, to determine what type of Down syndrome an individual has, someone has to count the chromosomes in a minimum of 200 cells throughout the body. I would be a horrible geneticist. All the intricacies associated with the science behind Down syndrome and how it affects our precious babies bodies at a microscopic level is so much greater than me.
No matter what is going on in their bodies microscopically or how many chromosomes they have, our babies are gifts from God and are no different than any other child; they just happen to have an extra chromosome, a “little something extra!”