Down’s syndrome is usually caused by an error in cell division. All people with Down’s syndrome have an extra, critical portion of chromosome 21 present in all or some of their cells. This additional genetic material alters the course of development and causes the characteristics associated with the syndrome.
Trisomy 21 - About 95 percent of the time, Down syndrome is caused by trisomy 21.
Mosaic Down syndrome - In this form children have some cells with an extra copy of chromosome 21.…