What Causes Down Syndrome?
Many people are curious about Down syndrome and what causes it. Is the condition hereditary? Is it a result of a parent's behavior or environment? Or are there other factors at play?
From what is currently known about Down syndrome, environmental factors and parental behavior do not appear to play a role. Most cases of this developmental disorder (approximately 92 percent) are caused by trisomy 21, meaning that each cell in the body has three copies of chromosome 21, instead of the usual two copies.
(Click Causes of Down Syndrome for a more in-depth discussion of this topic, including details on the cause of translocation Down syndrome.)