An official website of the United States government
Here’s how you know
Official websites use .gov A
.gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS A
lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
... normal two copies. Down syndrome (also known as trisomy21) is an example of a condition caused by trisomy . People with Down syndrome typically have three copies of chromosome 21 in ...