What Is Down Syndrome?

Down syndrome (also known as Down’s syndrome and Trisomy 21) is a genetic disorder that develops when a child inherits a third copy of chromosome 21. There are three types of Down syndrome that all share the same features with the delineation coming from when in development the third chromosome is attached to the genome, most commonly at conception. It is the most common chromosomal anomaly, seen in about 1 in 700 live births in the United States. There is no known direct cause of the triplication, though age does increase the chances from 0.1% at age 20 to 3% at age 45.