Editing Gene duplication (section)

===Subfunctionalization===

{{Main|Subfunctionalization}}

Another possible fate for duplicate genes is that both copies are equally free to accumulate degenerative mutations, so long as any defects are complemented by the other copy. This leads to a neutral "[[subfunctionalization]]" (a process of [[constructive neutral evolution]]) or DDC (duplication-degeneration-complementation) model,<ref name=Force_1999>{{cite journal | vauthors = Force A, Lynch M, Pickett FB, Amores A, Yan YL, Postlethwait J | title = Preservation of duplicate genes by complementary, degenerative mutations | journal = Genetics | volume = 151 | issue = 4 | pages = 1531–45 | date = April 1999 | doi = 10.1093/genetics/151.4.1531 | pmid = 10101175 | pmc = 1460548 }}</ref><ref name=Stoltzfus_1999>{{cite journal | vauthors = Stoltzfus A | title = On the possibility of constructive neutral evolution | journal = Journal of Molecular Evolution | volume = 49 | issue = 2 | pages = 169–81 | date = August 1999 | pmid = 10441669 | doi = 10.1007/PL00006540 | citeseerx = 10.1.1.466.5042 | bibcode = 1999JMolE..49..169S | s2cid = 1743092 }}</ref> in which the functionality of the original gene is distributed among the two copies.  Neither gene can be lost, as both now perform important non-redundant functions, but ultimately neither is able to achieve novel functionality.

Subfunctionalization can occur through neutral processes in which mutations accumulate with no detrimental or beneficial effects.  However, in some cases subfunctionalization can occur with clear adaptive benefits.  If an ancestral gene is [[pleiotropy|pleiotropic]] and performs two functions, often neither one of these two functions can be changed without affecting the other function.  In this way, partitioning the ancestral functions into two separate genes can allow for adaptive specialization of subfunctions, thereby providing an adaptive benefit.<ref name=DesMerais>{{cite journal | vauthors = Des Marais DL, Rausher MD | title = Escape from adaptive conflict after duplication in an anthocyanin pathway gene | journal = Nature | volume = 454 | issue = 7205 | pages = 762–5 | date = August 2008 | pmid = 18594508 | doi = 10.1038/nature07092 | bibcode = 2008Natur.454..762D | s2cid = 418964 }}</ref>