When I first had my son, I had no idea he was going to have Down Syndrome, and I had no idea what caused it. I knew some about it, as I had a friend with a sister who had Down Syndrome. So, my first question was, “Did I do something wrong?” One person even told some of my family that I must have been doing drugs. It’s funny to me that they were so uneducated about it, that they could not take the 10 minutes to get online and just do a quick search. You will quickly find that there is nothing that the mother could have or could not have done.
So again, this is just for education purposes and to have a quick reference guide for me to have in one place. My son has Trisomy 21, so that is what I have learned the most about. I know little about the other forms, but this is what I came up with:
- Our cells normally contain 23 pairs of chromosomes. Our parents each give us one of each chromosome to make up the 23 pairs.
- Down Syndrome results when abnormal cell division involving Chromosome 21 happens. There are 3 types of abnormal cell division.
- Trisomy 21 – Most Down Syndrome is caused by Trisomy 21. The cell division here happened during the development of the sperm cell or the egg cell.
- Mosaic Down Syndrome – This form of Down Syndrome is more rare. It’s caused by abnormal cell division after fertilization. That means not all cells have the extra copy of Chromosome 21.
- Translocation Down Syndrome – This happens when Chromosome 21 is translocated to another chromosome. It can happen before or at conception. There is also the additional material from Chromosome 21 attached to the translocated chromosome. This form is very uncommon and the only form that can be passed from parent to child.
Again, my disclaimer is that I know very little about Mosaic and Translocation Down Syndrome, but it all boils down to the fact that it is abnormal cell division, not something that someone did to cause it.