Down syndrome is quite simply the presence of an extra chromosome in the body’s cells. Instead of the usual 23 pairs, individuals who have Down Syndrome have an additional chromosome 21. Down Syndrome is not a disease, and the standard trisomy 21 type, is not a hereditary condition.
People with DS do have some learning difficulties but this varies enormously from individual to individual, just as the abilities of ordinary children vary. Certain physical characteristics can be common amongst people who have DS, and they are sometimes more prone to certain medical problems. There are a list of physical characteristics which Doctors use to determine if there may be a chance of a baby having DS and if the baby has a significant number of these indicators then a blood test is requested to establish for certain. Interestingly every characteristic found on ‘the list’ is spmething which can be found in ordinary babies too.
There are three types:
- Trisomy 21 in which all the cells have an extra chromosome 21. About 94% of people with Down Syndrome have Trisomy 21.
- Translocation in which extra chromosome 21 material is attached to another chromosome. Around 4% of people with Down Syndrome have this type.
- Mosaic or Mosaicism in which only some of the cells have an extra chromosome 21 (the proportion of cells with an extra chromosome can vary considerably and so the affect this has can vary accordingly). Only around 2% of people with Down Syndrome have this type.
The MOST important thing to remember is that everyone with DS is an individual, with their own character and personality, their own strengths and weaknesses.