Autosomes

Autosomes are the chromosomes that are not directly involved in determining an organism's sex. In humans, they constitute 22 pairs of homologous chromosomes, numbered 1 through 22, and they, together with the two sex chromosomes, form the diploid karyotype of 46 chromosomes. The autosomes are usually similar in size and gene content between the homologous pairs, and they pair and recombine during meiosis.

Most of the organism's genes are located on autosomes. They follow Mendelian inheritance patterns, with autosomal dominant, autosomal recessive, and, less commonly, co-dominant modes of inheritance. Because autosomes contain many essential genes, chromosomal abnormalities affecting autosomes can have significant developmental and medical consequences.

Autosomal abnormalities include aneuploidies such as trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome). Autosomal deletions, duplications, and other structural rearrangements can also cause disease and developmental issues.

In other species, the number and identity of autosomes can vary, but the concept remains that autosomes are the non-sex chromosomes. Many genetic tests, including karyotyping, fluorescence in situ hybridization, and microarray analysis, examine autosomes to detect numerical or structural abnormalities.