Types of Down's Syndrome
There are three different types of Down's Syndrome. Ninety-five per cent of people with Down's Syndrome have the type known as standard trisomy 21. This type of Down's Syndrome is always an accident of nature, and it can happen to anyone; why it occurs is unknown.
Approximately one in 100 people have the second type of Down's syndrome. They inherit the condition from either of their parents because of a translocation genetic anomaly.
The third type of Down's syndrome, also rare, is Mosaic Down's Syndrome, in which an extra chromosome 21 appears in only some of the cells.