Failure of two members of a chromosome pair to separate from one another during meiosis, causing both chromosomes to go to a single daughter cell. Meiotic nondisjunction is responsible for the extra chromosome 21 in trisomy 21 (Down syndrome) and for extra and missing chromosomes that cause other birth defects and many miscarriages.
- Melan- (prefix)
Prefix meaning dark or black. It comes from the Greek “melas”, black. Examples of terms containing melan- include melancholia, melanin, melanocytes, melanoma and melena.
An old term for depression.
The pigment that gives human skin, hair, and eyes their color. Dark-skinned people have more melanin in their skin than light-skinned people have. Melanin is produced by cells called melanocytes. It provides some protection again skin damage from the sun, and the melanocytes increase their production of melanin in response to sun exposure. Freckles, which […]
A cell in the skin that produces and contains the pigment melanin.