What is Euploidy and Aneuploidy?

Euploidy and aneuploidy are chromosomal variations that involve changes in the number of chromosomes in an organism.

Euploidy occurs when the number of entire chromosome sets changes. For example, normal humans are diploid (2n), meaning they have two sets of chromosomes. If an organism has one set (n), two sets (2n), or more complete sets like triploid (3n) or tetraploid (4n), it is called euploid. Euploidy is common in plants and often leads to larger cell size and vigorous growth.

Aneuploidy, on the other hand, is a condition in which there is an addition or loss of one or more specific chromosomes, not entire sets. It results from nondisjunction during meiosis. Examples include:

• Trisomy (2n + 1) — an extra chromosome, as in Down syndrome (Trisomy 21).
• Monosomy (2n - 1) — missing a chromosome, as in Turner syndrome (XO).

In short, euploidy affects entire sets of chromosomes, while aneuploidy affects individual chromosomes, often leading to developmental or genetic abnormalities.