Ploidy (Gr. Ploos - Multiple)

Ploidy is the number of identical or similar sets of chromosomes in a cell.

Ploidy determines the number of chromosomes in a cell. In most species, somatic tissue cells are diploid, that is, they contain two sets of chromosomes. Cells with one set of chromosomes (for example, sex cells) are called haploid.

Polyploidy is the presence of more than two sets of chromosomes. There are triploidy (3 sets), tetraploidy (4 sets), etc. Polyploid cells are often found in plants.

In humans, the normal ploidy of somatic cells is 2n (diploid). Deviations of ploidy lead to serious developmental disorders. For example, Down syndrome is associated with the presence of an extra chromosome (trisomy).

Thus, ploidy is an important characteristic of a cell, determining the number of chromosomes and influencing the development of the organism. Changes in ploidy often lead to pathological conditions.