Autosomes

Definition

Any chromosome that is not a sex chromosome (allosome). In diploid organisms, autosomes typically occur in homomorphic pairs with identical morphology and carry the bulk of the genome, including genes governing most somatic, physiological, and developmental traits unrelated to sexual differentiation. The collective DNA of autosomes is sometimes abbreviated atDNA or auDNA.

Etymology

From Greek autos (self) + soma (body), reflecting their presence in both sexes.

Example

In the fruit fly Drosophila melanogaster, the four pairs of autosomes (chromosomes 2, 3, and the small chromosome 4) carry genes for eye color, wing morphology, and metabolic enzymes, while sex-linked traits such as white eye color reside on the X and Y allosomes.

Synonyms

• non-sex chromosomes

Related Terms

• allosomes
• sex chromosomes
• karyotype
• diploidy
• sex determination
• chromosome pairing
• linkage mapping

Usage Notes

Contrasts with allosomes (sex chromosomes), which may be heteromorphic and carry sex-determining regions. Autosome number varies widely across arthropods—e.g., some ant species have reduced autosome complements due to chromosome fusion—making autosome counts useful in cytotaxonomy. In population genetics, 'autosomal' inheritance patterns differ from sex-linked or mitochondrial inheritance. The term is absolute, not relative; it does not imply any particular size or gene density.