What does trisomy refer to in genetic terms?

Trisomy refers to a condition in which an individual has three copies of a particular chromosome instead of the usual two. This leads to a total of 47 chromosomes instead of the normal 46. The presence of an extra chromosome can result in various developmental and physical challenges, often associated with specific syndromes like Down syndrome, which is trisomy 21.

In this context, having an extra chromosome directly corresponds to the definition of trisomy. Each chromosome pair typically comprises two copies, and trisomy indicates that one of these pairs has an additional copy, leading to the noted increase in chromosome number.