Autosomosomes

Autosomes are the chromosomes that do not determine sex. In humans, there are 22 pairs of autosomes (numbers 1 through 22), totaling 44 autosomal chromosomes, alongside a pair of sex chromosomes (X and Y) that determine biological sex. Autosomes carry the majority of genes and influence a wide range of traits and bodily functions.

Individuals inherit one copy of each autosome from each parent, creating two alleles for most autosomal genes. This biparental inheritance underlies common patterns of inheritance, including autosomal dominant and autosomal recessive traits. In autosomal dominant conditions, a single altered copy can cause disease, while autosomal recessive conditions require two copies of the alteration for the condition to be expressed. Examples of autosomal dominant disorders include Huntington disease and Marfan syndrome; autosomal recessive disorders include cystic fibrosis and phenylketonuria. Many traits, such as height or skin coloration, are polygenic, involving multiple autosomal genes and environmental factors.

Meiosis involves pairing and crossing over of homologous autosomes, which increases genetic diversity in offspring. Errors in autosome number or structure can lead to conditions such as Down syndrome (trisomy 21) or other aneuploidies and rearrangements.

Clinically, autosomal inheritance is evaluated through family history, genetic testing, and counseling. Because autosomes are present in two copies, carriers of autosomal recessive conditions may be asymptomatic but have a risk of passing the condition to offspring. Understanding autosomes is fundamental to genetics, evolutionary biology, and medicine.