Down’s syndrome (also called Down syndrome) is a genetic condition known as trisomy, where a person inherits an extra copy of one chromosome. People with the syndrome have three copies of chromosome 21 rather than two.
This additional genetic material changes the finely tuned balance of the body and results in characteristic physical and intellectual features.
There are three types of Down’s syndrome:
Regular trisomy 21 - all the cells have an extra chromosome 21. Around 94 per cent of people with Down’s syndrome have this type.
Translocation - the extra chromosome 21 material is attached to another chromosome and one of the parents may carry the translocated chromosome without any signs of the condition themselves. This accounts for around 4 per cent of cases.
Mosaic - only some of the cells have an extra chromosome 21. Around two per cent of people with Down’s have this type, which tends to result in milder features.
The severity of Down’s syndrome symptoms can vary from person to person. There is currently no cure for the condition. However, there are treatments that can help someone with the syndrome to lead an active and independent life.