It is a genetic condition caused when an unusual cell division result in an extra full or even partial copy of chromosome 21.

While Emma has Down syndrome — specifically a rare type called Mosaic Down syndrome — some people don’t believe it. “At the ...

The diminutive chromosome 21--the smallest of the human contingent, despite its number as next to last--is the fourth to be described. Its debut in mid-May attracted attention because 21 is a ...

Chromosome 21 is the smallest human chromosome, and procedures for examining human chromosomes were still being developed during the first part of the century. Many early cytologists had ...

Medically reviewed by Brigid Dwyer, MD Mosaic Down syndrome is a variant of Down syndrome. Down syndrome is a congenital (present at birth) genetic condition that occurs when a person has three copies ...

What is the structure of a chromosome? Why does the total number of chromosomes in a cell matter? Learn how chromosomes self-organize within single cells, and how these patterns help us detect ...

Researchers who study Down syndrome at the University of Colorado Boulder advocate for more inclusion on World Down Syndrome ...

Human biological sex is determined by the sex chromosomes X and Y. In most cases, females possess two X chromosomes, while males have one X and one Y. However, there is some evidence that the Y ...

World Down Syndrome Day is March 21 (or 3-21) to represent the third copy on a 21st chromosome. The event took place at a ...