Autosome

This article is about a type of chromosome. For the ancestral discovery method using autosomal DNA, see Genealogical DNA test § Geographic origin tests.

An autosome is any chromosome that is not a sex chromosome.[1] The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosomes is collectively known as atDNA or auDNA.[2]

For example, humans have a diploid genome that usually contains 22 pairs of autosomes and one allosome pair (46 chromosomes total). The autosome pairs are labeled with numbers (1–22 in humans) roughly in order of their sizes in base pairs, while allosomes are labelled with their letters.[3] By contrast, the allosome pair consists of two X chromosomes in females or one X and one Y chromosome in males. Unusual combinations XYY, XXY, XXX, XXXX, XXXXX or XXYY, among other irregular combinations, are known to occur and usually cause developmental abnormalities.

Autosomes still contain sexual determination genes even though they are not sex chromosomes. For example, the SRY gene on the Y chromosome encodes the transcription factor TDF and is vital for male sex determination during development. TDF functions by activating the SOX9 gene on chromosome 17, so mutations of the SOX9 gene can cause humans with an ordinary Y chromosome to develop as females.[4]

All human autosomes have been identified and mapped by extracting the chromosomes from a cell arrested in metaphase or prometaphase and then staining them with a type of dye (most commonly, Giemsa).[5] These chromosomes are typically viewed as karyograms for easy comparison. Clinical geneticists can compare the karyogram of an individual to a reference karyogram to discover the cytogenetic basis of certain phenotypes. For example, the karyogram of someone with Patau Syndrome would show that they possess three copies of chromosome 13. Karyograms and staining techniques can only detect large-scale disruptions to chromosomes—chromosomal aberrations smaller than a few million base pairs generally cannot be seen on a karyogram.[6]

Karyotype of human chromosomes
Female (XX) Male (XY)
There are two copies of each autosome (chromosomes 1–22) in both females and males. The sex chromosomes are different: There are two copies of the X-chromosome in females, but males have a single X-chromosome and a Y-chromosome.
  1. ^ Griffiths, Anthony J. F. (1999). An Introduction to genetic analysis. New York: W.H. Freeman. ISBN 978-0-7167-3771-1.
  2. ^ "Autosomal DNA - ISOGG Wiki". www.isogg.org. Archived from the original on 21 August 2017. Retrieved 28 April 2018.
  3. ^ "Autosome Definition(s)". Genetics Home Reference. Archived from the original on 2 January 2016. Retrieved 28 April 2018.
  4. ^ Foster JW, Dominguez-Steglich MA, Guioli S, Kwok C, Weller PA, Stevanović M, Weissenbach J, Mansour S, Young ID, Goodfellow PN (December 1994). "Complicate dysplasia and autosomal sex reversal caused by mutations in an SRY-related gene". Nature. 372 (6506): 525–30. Bibcode:1994Natur.372..525F. doi:10.1038/372525a0. PMID 7990924. S2CID 1472426.
  5. ^ "Chromosome mapping Facts, information, pictures". encyclopedia.com. Encyclopedia.com articles about Chromosome mapping. Archived from the original on 10 December 2015. Retrieved 4 December 2015.
  6. ^ Nussbaum RL, McInnes RR, Willard HF, Hamosh A, Thompson MW (2007). Thompson & Thompson Genetics in Medicine (7th ed.). Philadelphia, PA: Saunders/Elsevier. p. 69. ISBN 9781416030805.