Downs Syndrome also called Trisonomy 21, occurs when the 21st chromosome has a third chromosome instead of the usual 2 or pair.
Whats a Chromosome?
a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.Humans have 46 chromosome pairs
Ways that Downs Syndrome occurs
There are 3 different ways that Downs Syndrome can occur depending upon how the cells divide when first conceived:
- – Trisonomy 21 (95% of cases_ All cells of the body have the extra chromosome
- – Translocation (4-5% of cases) An extra copy of chromosome 21 is attached to another chromosome.
- – Mosaicism (less than 1% of cases) some cells have the usual 46chromosomes but others have the extra 21st