Definition:
The occurrence of an extra chromosome in a human. Down syndrome is the most common human trisomy. People with Down syndrome have an extra number 21 chromosome. This is sometimes written as 47,XX,+21 (female) or 47,XY,+21 (male).
Pronunciation: “Try””sew””me”
Examples:
A trisomy occurs when a person has three chromosomes instead of two. Down syndrome is also called trisomy 21 because individuals with Down syndrome have three number 21 chromosomes instead of two.
