Editing GC-content (section)

=== Coding sequences ===
Within a long region of genomic sequence, genes are often characterised by having a higher GC-content in contrast to the background GC-content for the entire genome.<ref name="pmid28261263">{{cite journal| author=Romiguier J, Roux C| title=Analytical Biases Associated with GC-Content in Molecular Evolution. | journal=Front Genet | year= 2017 | volume= 8 | issue=  | page= 16 | pmid=28261263 | doi=10.3389/fgene.2017.00016 | pmc=5309256 | doi-access=free }}</ref> There is evidence that the length of the [[coding region]] of a [[gene]] is directly proportional to higher G+C content.<ref>{{cite journal |vauthors=Pozzoli U, Menozzi G, Fumagalli M |title=Both selective and neutral processes drive GC content evolution in the human genome |journal=BMC Evol. Biol. |volume=8 |page=99 |year=2008 |issue=1 |pmid=18371205 |pmc=2292697 |doi=10.1186/1471-2148-8-99 |bibcode=2008BMCEE...8...99P |display-authors=etal |doi-access=free }}</ref> This has been pointed to the fact that the [[stop codon]] has a bias towards A and T nucleotides, and, thus, the shorter the sequence the higher the AT bias.<ref>{{cite journal |vauthors=Wuitschick JD, Karrer KM |title=Analysis of genomic G + C content, codon usage, initiator codon context and translation termination sites in ''Tetrahymena thermophila'' |journal=J. Eukaryot. Microbiol. |volume=46 |issue=3 |pages=239–47 |year=1999 |pmid=10377985 |doi=10.1111/j.1550-7408.1999.tb05120.x |s2cid=28836138 }}</ref>

Comparison of more than 1,000 [[orthologous]] genes in mammals showed marked within-genome variations of the [[codon|third-codon position]] GC content, with a range from less than 30% to more than 80%.<ref name="Romiguier2010"/>