According to CDC, babies are born with Down Syndrome because of an error in the cell division called “nondisjunction.” Nondisjunction is a result in an embryo with 3 copies of chromosomes instead of 2. The pair of 21 chromosomes in either the sperm or the egg fail to separate. The cause of the extra full or partial chromosomes are still unknown. Down Syndrome can be detected before or after birth.
“Birth Defects.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 27 Feb. 2018, www.cdc.gov/ncbddd/birthdefects/DownSyndrome.html
“Birth Defects.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 27 Feb. 2018, www.cdc.gov/ncbddd/birthdefects/DownSyndrome.html