Evolution Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! === Mutation === {{main|Mutation}} [[File:Gene-duplication.svg|thumb|upright|Duplication of part of a [[chromosome]]]] Mutations are changes in the DNA sequence of a cell's genome and are the ultimate source of genetic variation in all organisms.<ref name="Futuyma2017c">{{harvnb|Futuyma |Kirkpatrick |2017 |pp=79–102 |loc=Chapter 4: Mutation and Variation}}</ref> When mutations occur, they may alter the [[gene product|product of a gene]], or prevent the gene from functioning, or have no effect. About half of the mutations in the coding regions of protein-coding genes are deleterious — the other half are neutral. A small percentage of the total mutations in this region confer a fitness benefit.<ref>{{ cite journal | last = Keightley | first = PD | date = 2012 | title = Rates and fitness consequences of new mutations in humans | journal = Genetics | volume =190 | issue = 2 | pages = 295–304 | doi = 10.1534/genetics.111.134668 | pmid = 22345605 | pmc = 3276617 }}</ref> Some of the mutations in other parts of the genome are deleterious but the vast majority are neutral. A few are beneficial. Mutations can involve large sections of a chromosome becoming [[gene duplication|duplicated]] (usually by [[genetic recombination]]), which can introduce extra copies of a gene into a genome.<ref>{{cite journal |last1=Hastings |first1=P. J. |last2=Lupski |first2=James R. |author-link2=James R. Lupski |last3=Rosenberg |first3=Susan M. |last4=Ira |first4=Grzegorz |date=August 2009 |title=Mechanisms of change in gene copy number |journal=Nature Reviews Genetics |volume=10 |issue=8 |pages=551–564 |doi=10.1038/nrg2593 |issn=1471-0056 |pmc=2864001 |pmid=19597530}}</ref> Extra copies of genes are a major source of the raw material needed for new genes to evolve.<ref>{{harvnb|Carroll|Grenier|Weatherbee|2005}}{{page needed|date=December 2014}}</ref> This is important because most new genes evolve within [[gene family|gene families]] from pre-existing genes that share common ancestors.<ref>{{cite journal |last1=Harrison |first1=Paul M. |last2=Gerstein |first2=Mark |author-link2=Mark Bender Gerstein |date=17 May 2002 |title=Studying Genomes Through the Aeons: Protein Families, Pseudogenes and Proteome Evolution |journal=[[Journal of Molecular Biology]] |volume=318 |issue=5 |pages=1155–1174 |doi=10.1016/S0022-2836(02)00109-2 |issn=0022-2836 |pmid=12083509}}</ref> For example, the [[human eye]] uses four genes to make structures that sense light: three for [[Cone cell|colour vision]] and one for [[Rod cell|night vision]]; all four are descended from a single ancestral gene.<ref>{{cite journal |last=Bowmaker |first=James K. |s2cid=12851209 |title=Evolution of colour vision in vertebrates |date=May 1998 |journal=Eye |volume=12 |issue=3b |pages=541–547 |doi=10.1038/eye.1998.143 |issn=0950-222X |pmid=9775215|doi-access=free }}</ref> New genes can be generated from an ancestral gene when a duplicate copy mutates and acquires a new function. This process is easier once a gene has been duplicated because it increases the [[Gene redundancy|redundancy]] of the system; one gene in the pair can acquire a new function while the other copy continues to perform its original function.<ref>{{cite journal |last1=Gregory |first1=T. Ryan |author-link1=T. Ryan Gregory |last2=Hebert |first2=Paul D. N. |author-link2=Paul D. N. Hebert |date=April 1999 |title=The Modulation of DNA Content: Proximate Causes and Ultimate Consequences |url=http://genome.cshlp.org/content/9/4/317.full |journal=[[Genome Research]] |volume=9 |issue=4 |pages=317–324 |doi=10.1101/gr.9.4.317 |issn=1088-9051 |pmid=10207154 |s2cid=16791399 |access-date=11 December 2014 |url-status=live |archive-url=https://web.archive.org/web/20140823063412/http://genome.cshlp.org/content/9/4/317.full |archive-date=23 August 2014|doi-access=free }}</ref><ref>{{cite journal |last=Hurles |first=Matthew |title=Gene Duplication: The Genomic Trade in Spare Parts |date=13 July 2004 |journal=[[PLOS Biology]] |volume=2 |issue=7 |page=e206 |doi=10.1371/journal.pbio.0020206 |issn=1545-7885 |pmc=449868 |pmid=15252449 |doi-access=free }}</ref> Other types of mutations can even generate entirely new genes from previously noncoding DNA, a phenomenon termed [[de novo gene birth|''de novo'' gene birth]].<ref>{{cite journal |last1=Liu |first1=Na |last2=Okamura |first2=Katsutomo |last3=Tyler |first3=David M. |last4=Phillips |first4=Michael D. |last5=Chung |first5=Wei-Jen |last6=Lai |first6=Eric C |date=October 2008 |title=The evolution and functional diversification of animal microRNA genes |journal=Cell Research |volume=18 |issue=10 |pages=985–996 |doi=10.1038/cr.2008.278 |issn=1001-0602 |pmc=2712117 |pmid=18711447 |display-authors=3}}</ref><ref>{{cite journal |last=Siepel |first=Adam |author-link=Adam C. Siepel |date=October 2009 |title=Darwinian alchemy: Human genes from noncoding DNA |journal=Genome Research |volume=19 |issue=10 |pages=1693–1695 |doi=10.1101/gr.098376.109 |issn=1088-9051 |pmc=2765273 |pmid=19797681}}</ref> The generation of new genes can also involve small parts of several genes being duplicated, with these fragments then recombining to form new combinations with new functions ([[exon shuffling]]).<ref>{{cite journal |last1=Orengo |first1=Christine A. |last2=Thornton |first2=Janet M. |s2cid=7483470 |author-link2=Janet Thornton |date=July 2005 |title=Protein families and their evolution—a structural perspective |journal=[[Annual Review of Biochemistry]] |publisher=[[Annual Reviews (publisher)|Annual Reviews]] |volume=74 |pages=867–900 |doi=10.1146/annurev.biochem.74.082803.133029 |issn=0066-4154 |pmid=15954844}}</ref><ref>{{cite journal |last1=Long |first1=Manyuan |last2=Betrán |first2=Esther |last3=Thornton |first3=Kevin |last4=Wang |first4=Wen |date=November 2003 |title=The origin of new genes: glimpses from the young and old |journal=Nature Reviews Genetics |volume=4 |issue=11 |pages=865–875 |doi=10.1038/nrg1204 |issn=1471-0056 |pmid=14634634|s2cid=33999892 }}</ref> When new genes are assembled from shuffling pre-existing parts, [[protein domain|domains]] act as modules with simple independent functions, which can be mixed together to produce new combinations with new and complex functions.<ref>{{cite journal |last1=Wang |first1=Minglei |last2=Caetano-Anollés |first2=Gustavo |author-link2=Gustavo Caetano-Anolles |date=14 January 2009 |title=The Evolutionary Mechanics of Domain Organization in Proteomes and the Rise of Modularity in the Protein World |journal=[[Structure (journal)|Structure]] |volume=17 |issue=1 |pages=66–78 |doi=10.1016/j.str.2008.11.008 |issn=1357-4310 |pmid=19141283|doi-access=free }}</ref> For example, [[polyketide synthase]]s are large [[enzyme]]s that make [[antibiotic]]s; they contain up to 100 independent domains that each catalyse one step in the overall process, like a step in an assembly line.<ref>{{cite journal |last1=Weissman |first1=Kira J. |last2=Müller |first2=Rolf |date=14 April 2008 |title=Protein–Protein Interactions in Multienzyme Megasynthetases |journal=[[ChemBioChem]] |volume=9 |issue=6 |pages=826–848 |doi=10.1002/cbic.200700751 |issn=1439-4227 |pmid=18357594|s2cid=205552778 }}</ref> One example of mutation is [[wild boar]] piglets. They are camouflage coloured and show a characteristic pattern of dark and light longitudinal stripes. However, mutations in the ''[[melanocortin 1 receptor]]'' (''MC1R'') disrupt the pattern. The majority of pig breeds carry MC1R mutations disrupting wild-type colour and different mutations causing dominant black colouring.<ref>{{Cite journal |last=Andersson |first=Leif |date=2020 |title=Mutations in Domestic Animals Disrupting or Creating Pigmentation Patterns |journal=Frontiers in Ecology and Evolution |volume=8 |doi=10.3389/fevo.2020.00116 |issn=2296-701X|doi-access=free }}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). 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