What is Down Syndrome?

Down syndrome, also called DS, is a condition caused by a mutation in the chromosomes during cell division. This mutation is a random event – it is not caused by environmental factors or by anything the parents did. In most people with Down syndrome, this mutation results in an extra copy of Chromosome 21. The extra genetic material disrupts the normal course of development of the body and the brain. Down syndrome is the most frequent genetic cause of mild to moderate developmental delay.