Julie Jordan is an Editor at Large for PEOPLE. She has been with the brand for 27 years, writing cover stories and features and managing special issues including the Beautiful Issue and Sexiest Man ...

Medically reviewed by Nicholas R. Metrus, MD Key Takeaways Mosaic Down syndrome has some cells with three copies of chromosome 21, and some with two instead of all three.Only about 1% to 2% of people ...

Chromosomal aberrations are departures from the normal set of chromosomes either from an individual or from a species. All age group capable of reproduction are at risk of this, but however, research ...

Rare Chromosome Awareness Day, celebrated in June, is an opportunity to increase public knowledge about rare chromosome and gene disorders. These conditions can lead to various physical, developmental ...

Genes are segments of DNA (deoxyribonucleic acid) that are located inside every human cell. The DNA inside each cell is tightly coiled in structures called chromosomes. Each chromosome contains a ...

Sex chromosomes are chromosomes, or packages of DNA, that are found inside the nucleus of all of your cells. There are two different kinds: X and Y, which determine whether you’re biologically male ...

Sex determination at birth is decided on the chromosomes the baby has. A female has two X chromosomes, whereas a male has one X and one Y chromosome. According to Medline Plus, in every cell, humans ...

A massive global genetics study is reshaping how we understand mental illness—and why diagnoses so often pile up. By ...