Editing Mutation (section)

=== By inheritance ===
[[File:Portulaca grandiflora mutant1.jpg|thumb|right|A mutation has caused this [[Portulaca grandiflora|moss rose]] plant to produce flowers of different colours. This is a [[Somatic (biology)|somatic]] mutation that may also be passed on in the [[germline]].]]
In [[multicellular organism]]s with dedicated [[Gamete|reproductive cell]]s, mutations can be subdivided into [[germline mutation]]s, which can be passed on to descendants through their reproductive cells, and [[Somatic (biology)|somatic]] mutations (also called acquired mutations),<ref name="Somatic_cell">{{cite encyclopedia |encyclopedia=Genome Dictionary |title=Somatic cell genetic mutation |url=https://theodora.com/genetics/#somaticcellgeneticmutation |access-date=6 June 2010 |date=30 June 2007 |publisher=Information Technology Associates |location=Athens, Greece |url-status=dead |archive-url=https://web.archive.org/web/20100224074045/http://www.theodora.com/genetics/#somaticcellgeneticmutation |archive-date=24 February 2010 }}</ref> which involve cells outside the dedicated reproductive group and which are not usually transmitted to descendants.

Diploid organisms (e.g., humans) contain two copies of each gene—a paternal and a maternal allele. Based on the occurrence of mutation on each chromosome, we may classify mutations into three types. A [[wild type]] or homozygous non-mutated organism is one in which neither allele is mutated.
* A heterozygous mutation is a mutation of only one allele.
* A homozygous mutation is an identical mutation of both the paternal and maternal alleles.
* [[compound heterozygosity|Compound heterozygous]] mutations or a genetic compound consists of two different mutations in the paternal and maternal alleles.<ref>{{cite encyclopedia |encyclopedia=MedTerms |title=Compound heterozygote |url=http://www.medicinenet.com/script/main/art.asp?articlekey=33675 |access-date=9 October 2015 |date=14 June 2012 |publisher=[[WebMD]] |location=New York |url-status=dead |archive-url=https://web.archive.org/web/20160304123903/http://www.medicinenet.com/script/main/art.asp?articlekey=33675 |archive-date=4 March 2016 }}</ref>

==== Germline mutation ====
{{Further|Germline mutation}}
A germline mutation in the reproductive cells of an individual gives rise to a ''constitutional mutation'' in the offspring, that is, a mutation that is present in every cell. A constitutional mutation can also occur very soon after [[fertilization]], or continue from a previous constitutional mutation in a parent.<ref>{{cite web|url=http://www.daisyfund.org/rb/about/genetics.html|title=''RB1'' Genetics|website=Daisy's Eye Cancer Fund|location=Oxford, UK|archive-url=https://web.archive.org/web/20111126004753/http://www.daisyfund.org/rb/about/genetics.html|archive-date=26 November 2011|access-date=9 October 2015}}</ref> A germline mutation can be passed down through subsequent generations of organisms.

The distinction between germline and somatic mutations is important in animals that have a dedicated germline to produce reproductive cells. However, it is of little value in understanding the effects of mutations in plants, which lack a dedicated germline. The distinction is also blurred in those animals that [[asexual reproduction|reproduce asexually]] through mechanisms such as [[budding]], because the cells that give rise to the daughter organisms also give rise to that organism's germline.

A new germline mutation not inherited from either parent is called a '''''[[wikt:de novo|de novo]]'' mutation'''.

==== Somatic mutation ====
{{main|Somatic mutation}}

A change in the genetic structure that is not inherited from a parent, and also not passed to offspring, is called a [[somatic cell|somatic]] mutation''.<ref name="Somatic_cell" />'' Somatic mutations are not inherited by an organism's offspring because they do not affect the [[germline]]. However, they are passed down to all the progeny of a mutated cell within the same organism during mitosis. A major section of an organism therefore might carry the same mutation. These types of mutations are usually prompted by environmental causes, such as ultraviolet radiation or any exposure to certain harmful chemicals, and can cause diseases including cancer.''<ref>{{Cite encyclopedia|url=https://www.britannica.com/science/somatic-mutation|title=somatic mutation {{!}} genetics|access-date=31 March 2017|url-status=live|archive-url=https://web.archive.org/web/20170331122201/https://www.britannica.com/science/somatic-mutation|archive-date=31 March 2017|encyclopedia=Encyclopædia Britannica}}</ref>''

With plants, some somatic mutations can be propagated without the need for seed production, for example, by [[grafting]] and stem cuttings. These type of mutation have led to new types of fruits, such as the "Delicious" [[apple]] and the "Washington" navel [[Orange (fruit)|orange]].<ref>{{cite book | vauthors = Hartl L, Jones EW |url=https://archive.org/details/geneticsprincipl00hart/page/556|title=Genetics Principles and Analysis|publisher=Jones and Bartlett Publishers|year=1998|isbn=978-0-7637-0489-6|location=Sudbury, Massachusetts|pages=[https://archive.org/details/geneticsprincipl00hart/page/556 556]|url-access=registration}}</ref>

Human and mouse [[somatic cell]]s have a mutation rate more than ten times higher than the [[germline]] mutation rate for both species; mice have a higher rate of both somatic and germline mutations per [[cell division]] than humans. The disparity in mutation rate between the germline and somatic tissues likely reflects the greater importance of [[genome]] maintenance in the germline than in the soma.<ref name="Milholland">{{cite journal | vauthors = Milholland B, Dong X, Zhang L, Hao X, Suh Y, Vijg J | title = Differences between germline and somatic mutation rates in humans and mice | journal = Nature Communications | volume = 8 | pages = 15183 | date = May 2017 | pmid = 28485371 | pmc = 5436103 | doi = 10.1038/ncomms15183 | bibcode = 2017NatCo...815183M }}</ref>