There are three types of Down Syndrome

1. Trisomy 21: instead of the usual 2 copies of chromosome, there are three seperate copies of chromosome. about 95% of people with Down Syndrome have Trisomy 21, 2. Translocation Down Syndromethis account for a small 3% of people with Down Syndrome. this happens when a exra part of a whole chromosome 21 is present and is attached or trans-located to a different chromosome than being a seperate chrosome 21. 3. Mosiac Down Syndrome: this only count for 2% of people with Down Syndrome.mosiac means mixture or combination. so some children have their three copies of chrosome 21, but other cells have the typical two copies of chromosome 21.some chilldren with mosiac Down Syndrome may have fewer features of the condition due to ssome or many cells with typical numbers of chromosome.