Editing Mutagenesis (section)

==Distinction between a mutation and DNA damage==
DNA damage is an abnormal alteration in the structure of [[DNA]] that cannot, itself, be replicated when [[DNA replication|DNA replicates]]. In contrast, a [[mutation]] is a change in the [[nucleic acid sequence]] that can be replicated; hence, a mutation can be [[Heredity|inherited]] from one generation to the next. Damage can occur from chemical addition (adduct), or structural disruption to a base of DNA (creating an abnormal nucleotide or nucleotide fragment), or a break in one or both DNA strands. Such DNA damage may result in mutation. When DNA containing damage is replicated, an incorrect base may be inserted in the new complementary strand as it is being synthesized (see [[DNA repair#Translesion synthesis|DNA repair § Translesion synthesis]]). The incorrect insertion in the new strand will occur opposite the damaged site in the template strand, and this incorrect insertion can become a mutation (i.e. a changed base pair) in the next round of replication. Furthermore, double-strand breaks in DNA may be repaired by an inaccurate repair process, [[non-homologous end joining]], which produces mutations. Mutations can ordinarily be avoided if accurate [[DNA repair]] systems recognize DNA damage and repair it prior to completion of the next round of replication. At least 169 enzymes are either directly employed in DNA repair or influence DNA repair processes. Of these, 83 are directly employed in the 5 types of DNA repair processes indicated in the chart shown in [[DNA repair#Frequencies of epimutations in DNA repair genes|the article DNA repair]].

Mammalian nuclear DNA may sustain more than 60,000 damage episodes per cell per day, as listed with references in [[DNA damage (naturally occurring)]]. If left uncorrected, these adducts, after misreplication past the damaged sites, can give rise to mutations. In nature, the mutations that arise may be beneficial or deleterious—this is the driving force of evolution. An organism may acquire new traits through genetic mutation, but mutation may also result in impaired function of the genes and, in severe cases, causes the death of the organism. Mutation is also a major source for acquisition of [[Antimicrobial resistance|resistance to antibiotics]] in bacteria, and to antifungal agents in yeasts and molds.<ref name="Geisinger">{{Cite journal|last1=Geisinger|first1=Edward|last2=Vargas-Cuebas|first2=Germán|last3=Mortman|first3=Nadav J.|last4=Syal|first4=Sapna|last5=Dai|first5=Yunfei|last6=Wainwright|first6=Elizabeth L.|last7=Lazinski|first7=David|last8=Wood|first8=Stephen|last9=Zhu|first9=Zeyu|date=2019-06-11|editor-last=Miller|editor-first=Samuel I.|title=The Landscape of Phenotypic and Transcriptional Responses to Ciprofloxacin in Acinetobacter baumannii : Acquired Resistance Alleles Modulate Drug-Induced SOS Response and Prophage Replication|journal=mBio|volume=10|issue=3|doi=10.1128/mBio.01127-19|issn=2150-7511|pmc=6561030|pmid=31186328}}</ref><ref name=":0">{{Cite journal|last1=Quinto-Alemany|first1=David|last2=Canerina-Amaro|first2=Ana|last3=Hernández-Abad|first3=Luís G.|last4=Machín|first4=Félix|last5=Romesberg|first5=Floyd E.|last6=Gil-Lamaignere|first6=Cristina|date=2012-07-31|editor-last=Sturtevant|editor-first=Joy|title=Yeasts Acquire Resistance Secondary to Antifungal Drug Treatment by Adaptive Mutagenesis|journal=PLOS ONE|volume=7|issue=7|pages=e42279|bibcode=2012PLoSO...742279Q|doi=10.1371/journal.pone.0042279|issn=1932-6203|pmc=3409178|pmid=22860105|doi-access=free}}</ref> In a laboratory setting, mutagenesis is a useful technique for generating mutations that allows the functions of genes and gene products to be examined in detail, producing proteins with improved characteristics or novel functions, as well as mutant strains with useful properties. Initially, the ability of radiation and chemical mutagens to cause mutation was exploited to generate random mutations, but later techniques were developed to introduce specific mutations.

In humans, an average of 60 new mutations are transmitted from parent to offspring. Human males, however, tend to pass on more mutations depending on their age, transmitting an average of two new mutations to their progeny with every additional year of their age.<ref>{{cite web|last=Jha|first=Alok|date=22 August 2012|title=Older fathers pass on more genetic mutations, study shows|url=https://www.theguardian.com/science/2012/aug/22/older-fathers-genetic-mutations-research|website=The Guardian}}</ref><ref>{{cite journal|last1=Kong|first1=A.|last2=Frigge|first2=M. L.|last3=Masson|first3=G.|last4=Besenbacher|first4=S.|last5=Sulem|first5=P.|last6=Magnusson|first6=G.|last7=Gudjonsson|first7=S. A.|last8=Sigurdsson|first8=A.|last9=Jonasdottir|first9=A.|last10=Jonasdottir|first10=A.|last11=Wong|first11=W. S.|year=2012|title=Rate of de novo mutations and the importance of father's age to disease risk|journal=Nature|volume=488|issue=7412|pages=471–475|bibcode=2012Natur.488..471K|doi=10.1038/nature11396|pmc=3548427|pmid=22914163|last19=Magnusson|last18=Helgason|first18=A.|last21=Stefansson|first19=O. T.|last20=Thorsteinsdottir|first20=U.|last17=Gudbjartsson|first17=D. F.|last15=Helgason|first16=G.|last16=Thorleifsson|first15=H.|first14=S.|last14=Steinberg|first13=G. B.|last13=Walters|first12=G.|last12=Sigurdsson|first21=K.}}</ref>