Mutation

A tulip flower exhibiting a partially yellow petal because of a mutation in its genes.

In biology, a mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements.[1]

Mutations result from errors during DNA replication (especially during meiosis) or other types of damage to DNA (such as may be caused by exposure to radiation or carcinogens), which then may undergo error-prone repair (especially microhomology-mediated end joining[2]), or cause an error during other forms of repair,[3][4] or else may cause an error during replication (translesion synthesis). Mutations may also result from insertion or deletion of segments of DNA due to mobile genetic elements.[5][6][7] Mutations may or may not produce discernible changes in the observable characteristics (phenotype) of an organism. Mutations play a part in both normal and abnormal biological processes including: evolution, cancer, and the development of the immune system, including junctional diversity.

The genomes of RNA viruses are based on RNA rather than DNA. The RNA viral genome can be double stranded (as in DNA) or single stranded. In some of these viruses (such as the single stranded human immunodeficiency virus) replication occurs quickly and there are no mechanisms to check the genome for accuracy. This error-prone process often results in mutations.

Mutation can result in many different types of change in sequences. Mutations in genes can either have no effect, alter the product of a gene, or prevent the gene from functioning properly or completely. Mutations can also occur in nongenic regions. One study on genetic variations between different species of Drosophila suggests that, if a mutation changes a protein produced by a gene, the result is likely to be harmful, with an estimated 70 percent of amino acid polymorphisms that have damaging effects, and the remainder being either neutral or marginally beneficial.[8] Due to the damaging effects that mutations can have on genes, organisms have mechanisms such as DNA repair to prevent or correct mutations by reverting the mutated sequence back to its original state.[5]

Description

Mutations can involve the duplication of large sections of DNA, usually through genetic recombination.[9] These duplications are a major source of raw material for evolving new genes, with tens to hundreds of genes duplicated in animal genomes every million years.[10] Most genes belong to larger gene families of shared ancestry, detectable by their sequence homology.[11] Novel genes are produced by several methods, commonly through the duplication and mutation of an ancestral gene, or by recombining parts of different genes to form new combinations with new functions.[12][13]

Here, protein domains act as modules, each with a particular and independent function, that can be mixed together to produce genes encoding new proteins with novel properties.[14] For example, the human eye uses four genes to make structures that sense light: three for cone cell or color vision and one for rod cell or night vision; all four arose from a single ancestral gene.[15] Another advantage of duplicating a gene (or even an entire genome) is that this increases engineering redundancy; this allows one gene in the pair to acquire a new function while the other copy performs the original function.[16][17] Other types of mutation occasionally create new genes from previously noncoding DNA.[18][19]

Changes in chromosome number may involve even larger mutations, where segments of the DNA within chromosomes break and then rearrange. For example, in the Homininae, two chromosomes fused to produce human chromosome 2; this fusion did not occur in the lineage of the other apes, and they retain these separate chromosomes.[20] In evolution, the most important role of such chromosomal rearrangements may be to accelerate the divergence of a population into new species by making populations less likely to interbreed, thereby preserving genetic differences between these populations.[21]

Sequences of DNA that can move about the genome, such as transposons, make up a major fraction of the genetic material of plants and animals, and may have been important in the evolution of genomes.[22] For example, more than a million copies of the Alu sequence are present in the human genome, and these sequences have now been recruited to perform functions such as regulating gene expression.[23] Another effect of these mobile DNA sequences is that when they move within a genome, they can mutate or delete existing genes and thereby produce genetic diversity.[6]

Nonlethal mutations accumulate within the gene pool and increase the amount of genetic variation.[24] The abundance of some genetic changes within the gene pool can be reduced by natural selection, while other "more favorable" mutations may accumulate and result in adaptive changes.

Prodryas persephone, a Late Eocene butterfly

For example, a butterfly may produce offspring with new mutations. The majority of these mutations will have no effect; but one might change the color of one of the butterfly's offspring, making it harder (or easier) for predators to see. If this color change is advantageous, the chances of this butterfly's surviving and producing its own offspring are a little better, and over time the number of butterflies with this mutation may form a larger percentage of the population.

Neutral mutations are defined as mutations whose effects do not influence the fitness of an individual. These can increase in frequency over time due to genetic drift. It is believed that the overwhelming majority of mutations have no significant effect on an organism's fitness.[25][26][better source needed] Also, DNA repair mechanisms are able to mend most changes before they become permanent mutations, and many organisms have mechanisms for eliminating otherwise-permanently mutated somatic cells.

Beneficial mutations can improve reproductive success.[27][28]

Other Languages
العربية: طفرة (أحياء)
asturianu: Mutación
azərbaycanca: Mutasiya
Bân-lâm-gú: Tu̍t-piàn
беларуская: Мутацыя
беларуская (тарашкевіца)‎: Мутацыя
български: Мутация
bosanski: Mutacija
català: Mutació
čeština: Mutace
dansk: Mutation
Deutsch: Mutation
eesti: Mutatsioon
Ελληνικά: Μετάλλαξη
español: Mutación
Esperanto: Mutacio
euskara: Mutazio
فارسی: جهش
Gaeilge: Sóchán
galego: Mutación
한국어: 돌연변이
հայերեն: Մուտացիա
hrvatski: Mutacija
Ido: Mutaco
Bahasa Indonesia: Mutasi
íslenska: Stökkbreyting
עברית: מוטציה
Basa Jawa: Mutasi
ಕನ್ನಡ: ವ್ಯತ್ಯಯನ
ქართული: მუტაცია
қазақша: Мутация
Kreyòl ayisyen: Mitasyon
Кыргызча: Мутация
latviešu: Mutācija
lietuvių: Mutacija
magyar: Mutáció
македонски: Мутација
Bahasa Melayu: Mutasi
монгол: Мутац
Nederlands: Mutatie (biologie)
日本語: 突然変異
Nordfriisk: Mutatjuun
norsk: Mutasjon
norsk nynorsk: Mutasjon
oʻzbekcha/ўзбекча: Mutatsiya
ਪੰਜਾਬੀ: ਮਿਊਟੇਸ਼ਨ
polski: Mutacja
português: Mutação
русский: Мутация
Scots: Mutation
shqip: Mutacioni
Simple English: Mutation
slovenčina: Mutácia (genetika)
slovenščina: Mutacija
کوردی: بازدان
српски / srpski: Мутација
srpskohrvatski / српскохрватски: Mutacija
suomi: Mutaatio
svenska: Mutation
Tagalog: Mutasyon
Türkçe: Mutasyon
українська: Мутація
اردو: طَفرَہ
Tiếng Việt: Đột biến sinh học
Winaray: Mutasyon
吴语: 突变
ייִדיש: מוטאציע
粵語: 基因突變
Zazaki: Mutasyon
中文: 突变