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{{short description|Phenotypically-different organism resulting from a mutation}}
{{other uses}}
{{other uses}}
{{refimprove|date=August 2017}}
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[[Image:Blue-lobster.jpg|220px|thumb|right|The [[American lobster#Coloration|blue lobster]], an example of a mutant]]
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[[Image:Physcomitrella knockout mutants.JPG|thumb|right|220px|Wild-type [[Physcomitrella patens|''Physcomitrella'']] and [[knockout moss]]es: Deviating phenotypes induced in gene-disruption library transformants. ''Physcomitrella'' wild-type and transformed plants were grown on minimal Knop medium to induce differentiation and development of [[gametophore]]s. For each [[plant]], an overview (upper row, scale bar corresponds to 1 mm) and a close-up (bottom row, scale bar equals 0.5 mm) is shown. A, [[Haploid]] wild-type moss plant completely covered with leafy gametophores and close-up of wild-type leaf. B–E, Different mutants.<ref>Egener et al. BMC Plant Biology 2002 2:6 {{doi|10.1186/1471-2229-2-6}}</ref>]]


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In [[biology]], and especially in [[genetics]], a '''mutant''' is an organism or a new genetic character arising or resulting from an instance of [[mutation]], which is generally an alteration of the [[DNA]] sequence of the [[genome]] or [[chromosome]] of an [[organism]]. It is a characteristic that would not be observed naturally in a specimen. The term mutant is also applied to a [[virus]] with an alteration in its [[Nucleic acid sequence|nucleotide sequence]] whose [[genome]] is in the [[Nuclear gene|nuclear genome]]. The natural occurrence of genetic mutations is integral to the process of [[evolution]]. The study of mutants is an integral part of biology; by understanding the effect that a mutation in a gene has, it is possible to establish the normal function of that gene.<ref>[http://www.pnas.org/content/68/9/2112.abstract Clock Mutants of ''Drosophila melanogaster'']</ref>
⚫
[[Image:Blue-lobster.jpg|200px|thumb|The [[American lobster#Mutations|blue lobster]] is an example of a mutant.]]
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[[Image:Physcomitrella knockout mutants.JPG|thumb|''Wild-type [[Physcomitrella patens|Physcomitrella]] and [[Knockout Moss|knockout mosses]]'': Deviating phenotypes induced in gene-disruption library transformants. Physcomitrella wild-type and transformed plants were grown on minimal Knop medium to induce differentiation and development of [[gametophore]]s. For each [[plant]], an overview (upper row, scale bar corresponds to 1 mm) and a close-up (bottom row, scale bar equals 0.5 mm) is shown. A, [[Haploid]] wild-type moss plant completely covered with leafy gametophores and close-up of wild-type leaf. B-D, Different Mutants.<ref>Egener et al. BMC Plant Biology 2002 2:6 {{DOI|10.1186/1471-2229-2-6}}</ref>]]


==Mutants arise by mutation==
⚫
In [[biology]] and especially [[genetics]], a '''mutant''' is an organism or a new genetic character arising or resulting from an instance of [[mutation]], which is a base-pair sequence change within the [[DNA]] of a [[gene]] or [[chromosome]] of an [[organism]]. The natural occurrence of genetic mutations is integral to the process of [[evolution]]. The study of mutants is an integral part of biology; by understanding the effect that a mutation in a gene has, it is possible to establish the normal function of that gene.<ref>http://www.pnas.org/content/68/9/2112.abstract Clock Mutants of ''Drosophila melanogaster''</ref>
Mutants arise by [[mutation]]s occurring in pre-existing [[genome]]s as a result of errors of [[DNA replication]] or errors of [[DNA repair]]. Errors of replication often involve [[DNA repair#translesion synthesis|translesion synthesis]] by a [[DNA polymerase#Polymerases η, ι and κ (eta, iota, and kappa)|DNA polymerase]] when it encounters and bypasses a damaged base in the template strand.<ref name="pmid19258535">{{cite journal |vauthors=Waters LS, Minesinger BK, Wiltrout ME, D'Souza S, Woodruff RV, Walker GC |title=Eukaryotic translesion polymerases and their roles and regulation in DNA damage tolerance |journal=Microbiol. Mol. Biol. Rev. |volume=73 |issue=1 |pages=134–54 |date=March 2009 |pmid=19258535 |pmc=2650891 |doi=10.1128/MMBR.00034-08 }}</ref> A [[DNA damage (naturally occurring)|DNA damage]] is an abnormal chemical structure in DNA, such as a strand break or an oxidized base, whereas a mutation, by contrast, is a change in the sequence of standard base pairs. Errors of repair occur when repair processes inaccurately replace a damaged DNA sequence. The DNA repair process [[microhomology-mediated end joining]] is particularly error-prone.<ref name="pmid18809224">{{cite journal |vauthors=McVey M, Lee SE |title=MMEJ repair of double-strand breaks (director's cut): deleted sequences and alternative endings |journal=Trends Genet. |volume=24 |issue=11 |pages=529–38 |date=November 2008 |pmid=18809224 |pmc=5303623 |doi=10.1016/j.tig.2008.08.007 }}</ref><ref name="pmid23610439">{{cite journal |vauthors=Truong LN, Li Y, Shi LZ, Hwang PY, He J, Wang H, Razavian N, Berns MW, Wu X |title=Microhomology-mediated End Joining and Homologous Recombination share the initial end resection step to repair DNA double-strand breaks in mammalian cells |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=110 |issue=19 |pages=7720–5 |date=May 2013 |pmid=23610439 |pmc=3651503 |doi=10.1073/pnas.1213431110 |bibcode=2013PNAS..110.7720T |doi-access=free }}</ref>

==Mutation info==
In some organisms mutants can be created by [[gene targeting]] to assess the function of any given gene. This experimental approach is called [[reverse genetics]].<ref>[[Ralf Reski]] (1998): Physcomitrella and Arabidopsis: the David and Goliath of
reverse genetics. Trends in Plant Science 3, 209-210 {{DOI|10.1016/S1360-1385(98)01257-6}}</ref>
For example, a collection of [[Knockout Moss|knockout-moss]] mutants can be used to identify genes with so far unknown functions.<ref>Egener et al. BMC Plant Biology 2002 2:6 {{DOI|10.1186/1471-2229-2-6}}</ref>


==Etymology==
==Etymology==
Although not all mutations have a noticeable [[phenotypic]] effect, the common usage of the word "mutant" is generally a [[pejorative]] term only used for noticeable mutations.<ref>Mutant. (n.d.). ''The American Heritage Dictionary of the English Language'', Fourth Edition. Retrieved March 05, 2008, from Dictionary.com website: http://dictionary.reference.com/browse/mutant</ref> Previously, people used the word "'''sport'''" (related to [[wikt:spurt|spurt]]) to refer to abnormal specimens. The scientific usage is broader, referring to any organism differing from the [[wild type]].
Although not all mutations have a noticeable [[phenotypic]] effect, the common usage of the word "mutant" is generally a [[pejorative]] term, only used for genetically or phenotypically noticeable mutations.<ref name=":0">[http://dictionary.reference.com/browse/mutant Mutant. (n.d.). ''The American Heritage Dictionary of the English Language'', Fourth Edition. Retrieved March 05, 2008, from Dictionary.com]</ref> Previously, people used the word "'''sport'''" (related to [[wikt:spurt|spurt]]) to refer to abnormal specimens. The scientific usage is broader, referring to any organism differing from the [[wild type]]. The word finds its origin in the Latin term mūtant- (stem of mūtāns), which means "to change".<ref name=":0" />


Mutants should not be confused with organisms born with [[Developmental abnormality|developmental abnormalities]], which are caused by errors during [[morphogenesis]]. In a developmental abnormality, the DNA of the organism is unchanged and the abnormality cannot be passed on to progeny. [[Conjoined twins]] are the result of developmental abnormalities.
Mutants should not be confused with organisms born with [[Developmental abnormality|developmental abnormalities]], which are caused by errors during [[morphogenesis]]. In a developmental abnormality, the DNA of the organism is unchanged and the abnormality cannot be passed on to progeny. [[Conjoined twins]] are the result of developmental abnormalities.


Chemicals that cause developmental abnormalities are called [[teratogen]]s; these may also cause mutations, but their effect on development is not related to mutations. Chemicals that induce mutations are called [[mutagen]]s. Most mutagens are also considered to be [[carcinogen]]s.
Chemicals that cause developmental abnormalities are called [[teratogen]]s; these may also cause mutations, but their effect on development is not related to mutations. Chemicals that induce mutations are called [[mutagen]]s. Most mutagens are also considered to be [[carcinogen]]s.

==Epigenetic alterations==
[[Mutation]]s are distinctly different from [[epigenetics|epigenetic]] alterations, although they share some common features. Both arise as a [[chromosome|chromosomal]] alteration that can be replicated and passed on to subsequent cell generations. Both, when occurring within a gene, may silence expression of the gene. Whereas mutant cell lineages arise as a change in the sequence of standard bases, epigenetically altered cell lineages retain the sequence of standard bases but have gene sequences with changed levels of expression that can be passed down to subsequent cell generations. Epigenetic alterations include [[DNA methylation|methylation]] of [[CpG site#Methylation of CpG islands stably silences genes|CpG islands]] of a gene [[Promoter (genetics)|promoter]] as well as specific chromatin histone modifications. Faulty repair of chromosomes at sites of DNA damage can give rise both to mutant cell lineages<ref name="pmid18809224">{{cite journal |vauthors=McVey M, Lee SE |title=MMEJ repair of double-strand breaks (director's cut): deleted sequences and alternative endings |journal=Trends Genet. |volume=24 |issue=11 |pages=529–38 |date=November 2008 |pmid=18809224 |pmc=5303623 |doi=10.1016/j.tig.2008.08.007 }}</ref> and/or [[DNA methylation in cancer#Methylation of CpG islands in promoters stably silences genes|epigenetically altered]] cell lineages.<ref name="pmid27259203">{{cite journal |vauthors=Dabin J, Fortuny A, Polo SE |title=Epigenome Maintenance in Response to DNA Damage |journal=Mol. Cell |volume=62 |issue=5 |pages=712–27 |date=June 2016 |pmid=27259203 |pmc=5476208 |doi=10.1016/j.molcel.2016.04.006 }}</ref>


==See also==
==See also==
* [[Evolution]]
* [[Mutant (fictional)|Mutants of Fiction]]
* [[Genetic engineering]]
* [[Genetically modified organism]]
* [[Mutants in fiction]]
* [[Mutationism]]
* [[Synthetic lethality]]
* [[Synthetic viability]]


==References==
==References==
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==External links==
==External links==
{{Wikiquote}}
* [http://www.mun.ca/biology/scarr/Antennapedia_mutant.htm Antennapedia mutant]
* [https://www.mun.ca/biology/scarr/Antennapedia_mutant.htm Antennapedia mutant]


[[Category:Evolutionary biology]]
[[Category:Evolutionary biology]]
[[Category:Classical genetics]]
[[Category:Classical genetics]]
[[Category:Mutation]]

Latest revision as of 22:02, 8 October 2024

For other uses, see Mutant (disambiguation).
The blue lobster, an example of a mutant
Wild-type Physcomitrella and knockout mosses: Deviating phenotypes induced in gene-disruption library transformants. Physcomitrella wild-type and transformed plants were grown on minimal Knop medium to induce differentiation and development of gametophores. For each plant, an overview (upper row, scale bar corresponds to 1 mm) and a close-up (bottom row, scale bar equals 0.5 mm) is shown. A, Haploid wild-type moss plant completely covered with leafy gametophores and close-up of wild-type leaf. B–E, Different mutants.[1]

In biology, and especially in genetics, a mutant is an organism or a new genetic character arising or resulting from an instance of mutation, which is generally an alteration of the DNA sequence of the genome or chromosome of an organism. It is a characteristic that would not be observed naturally in a specimen. The term mutant is also applied to a virus with an alteration in its nucleotide sequence whose genome is in the nuclear genome. The natural occurrence of genetic mutations is integral to the process of evolution. The study of mutants is an integral part of biology; by understanding the effect that a mutation in a gene has, it is possible to establish the normal function of that gene.[2]

Mutants arise by mutation

[edit]

Mutants arise by mutations occurring in pre-existing genomes as a result of errors of DNA replication or errors of DNA repair. Errors of replication often involve translesion synthesis by a DNA polymerase when it encounters and bypasses a damaged base in the template strand.[3] A DNA damage is an abnormal chemical structure in DNA, such as a strand break or an oxidized base, whereas a mutation, by contrast, is a change in the sequence of standard base pairs. Errors of repair occur when repair processes inaccurately replace a damaged DNA sequence. The DNA repair process microhomology-mediated end joining is particularly error-prone.[4][5]

Etymology

[edit]

Although not all mutations have a noticeable phenotypic effect, the common usage of the word "mutant" is generally a pejorative term, only used for genetically or phenotypically noticeable mutations.[6] Previously, people used the word "sport" (related to spurt) to refer to abnormal specimens. The scientific usage is broader, referring to any organism differing from the wild type. The word finds its origin in the Latin term mūtant- (stem of mūtāns), which means "to change".[6]

Mutants should not be confused with organisms born with developmental abnormalities, which are caused by errors during morphogenesis. In a developmental abnormality, the DNA of the organism is unchanged and the abnormality cannot be passed on to progeny. Conjoined twins are the result of developmental abnormalities.

Chemicals that cause developmental abnormalities are called teratogens; these may also cause mutations, but their effect on development is not related to mutations. Chemicals that induce mutations are called mutagens. Most mutagens are also considered to be carcinogens.

Epigenetic alterations

[edit]

Mutations are distinctly different from epigenetic alterations, although they share some common features. Both arise as a chromosomal alteration that can be replicated and passed on to subsequent cell generations. Both, when occurring within a gene, may silence expression of the gene. Whereas mutant cell lineages arise as a change in the sequence of standard bases, epigenetically altered cell lineages retain the sequence of standard bases but have gene sequences with changed levels of expression that can be passed down to subsequent cell generations. Epigenetic alterations include methylation of CpG islands of a gene promoter as well as specific chromatin histone modifications. Faulty repair of chromosomes at sites of DNA damage can give rise both to mutant cell lineages[4] and/or epigenetically altered cell lineages.[7]

See also

[edit]

References

[edit]
  1. ^ Egener et al. BMC Plant Biology 2002 2:6 doi:10.1186/1471-2229-2-6
  2. ^ Clock Mutants of Drosophila melanogaster
  3. ^ Waters LS, Minesinger BK, Wiltrout ME, D'Souza S, Woodruff RV, Walker GC (March 2009). "Eukaryotic translesion polymerases and their roles and regulation in DNA damage tolerance". Microbiol. Mol. Biol. Rev. 73 (1): 134–54. doi:10.1128/MMBR.00034-08. PMC 2650891. PMID 19258535.
  4. ^ a b McVey M, Lee SE (November 2008). "MMEJ repair of double-strand breaks (director's cut): deleted sequences and alternative endings". Trends Genet. 24 (11): 529–38. doi:10.1016/j.tig.2008.08.007. PMC 5303623. PMID 18809224.
  5. ^ Truong LN, Li Y, Shi LZ, Hwang PY, He J, Wang H, Razavian N, Berns MW, Wu X (May 2013). "Microhomology-mediated End Joining and Homologous Recombination share the initial end resection step to repair DNA double-strand breaks in mammalian cells". Proc. Natl. Acad. Sci. U.S.A. 110 (19): 7720–5. Bibcode:2013PNAS..110.7720T. doi:10.1073/pnas.1213431110. PMC 3651503. PMID 23610439.
  6. ^ a b Mutant. (n.d.). The American Heritage Dictionary of the English Language, Fourth Edition. Retrieved March 05, 2008, from Dictionary.com
  7. ^ Dabin J, Fortuny A, Polo SE (June 2016). "Epigenome Maintenance in Response to DNA Damage". Mol. Cell. 62 (5): 712–27. doi:10.1016/j.molcel.2016.04.006. PMC 5476208. PMID 27259203.
[edit]
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