1. Down’s syndrome is caused due to aneuploidy.
2. Aneuploidy is due to non-disjunction of chromosome at the time of gamete formation during meiosis. Due to nondisjunction, chromosomes fail to separate.
3. In addition to a homologous pair of 21st chromosome there is an extra 21st, therefore it is called trisomy (2n + 1) of 21st chromosome.
