Chromosomenantal

Chromosomenantal is a term used in genetics to denote the chromosomal number or complement of a cell or organism. It specifies the total count of chromosomes present in a nucleus, including the diploid set (2n) in somatic cells and the haploid set (n) in gametes.

In humans and many other species, the chromosomenantal is species-specific and serves as a basic descriptor of genome organization. Humans have 46 chromosomes in somatic cells (2n=46) and 23 in gametes (n=23).

Methods to determine the chromosomenantal include classical karyotyping with chromosome staining, fluorescence in situ hybridization (FISH), flow cytometry of DNA content, and sequencing-based copy-number analyses.

Clinically, deviations from the normal chromosomenantal—aneuploidies or polyploidy—underlie many developmental disorders and cancers. Examples include trisomy 21 (Down syndrome), trisomy 18, trisomy 13, monosomy X (Turner syndrome), and polysomy X or XXX.

In evolution and population genetics, chromosomenantal variation arises from chromosomal fusions and fissions, leading to karyotype diversity across taxa. In plants, polyploidy (e.g., tetraploidy) frequently increases chromosomenantal, contributing to speciation.

See also karyotype, ploidy, aneuploidy, chromosomal aberration.