Why is Downs syndrome referred to as a “genetic condition”?
The human body is made up of cells. Each cell is a like tiny factory, which makes the materials, needed for growth and maintenance of the body. All cells contain a nucleus in which genes are stored. Genes are grouped along rod-like structures called chromosomes. Usually, the nucleus of each cell contains 23 pairs of chromosomes, 23 we inherit from our mother and 23 we inherit from our father. In people with Down’s syndrome the cells contain 47 chromosomes, an extra copy of chromosome 21. This additional genetic material results in Down’s syndrome. There are three types of Down’s syndrome: • Trisomy 21 – in which all the cells have an extra chromosome 21. About 94% of people with Down’s syndrome will have this type • Translocation – in which extra chromosome 21 material is attached to another chromosome. Around 4% of people with Down’s syndrome have this type. • Mosaic – in which only some of the cells have an extra chromosome 21. About 2% of people with Down’s syndrome have this type.
