Editing Mutation (section)

=== Role in carcinogenesis ===
{{See also|Carcinogenesis}}
On the other hand, a mutation may occur in a somatic cell of an organism. Such mutations will be present in all descendants of this cell within the same organism. The accumulation of certain mutations over generations of somatic cells is part of cause of [[malignant transformation]], from normal cell to cancer cell.<ref>{{cite journal|vauthors=Ionov Y, Peinado MA, Malkhosyan S, Shibata D, Perucho M|s2cid=4254940|date=June 1993|title=Ubiquitous somatic mutations in simple repeated sequences reveal a new mechanism for colonic carcinogenesis|journal=Nature|volume=363|issue=6429|pages=558–61|bibcode=1993Natur.363..558I|doi=10.1038/363558a0|pmid=8505985}}</ref>

Cells with heterozygous loss-of-function mutations (one good copy of gene and one mutated copy) may function normally with the unmutated copy until the good copy has been spontaneously somatically mutated. This kind of mutation happens often in living organisms, but it is difficult to measure the rate. Measuring this rate is important in predicting the rate at which people may develop cancer.<ref>{{cite journal | vauthors = Araten DJ, Golde DW, Zhang RH, Thaler HT, Gargiulo L, Notaro R, Luzzatto L | title = A quantitative measurement of the human somatic mutation rate | journal = Cancer Research | volume = 65 | issue = 18 | pages = 8111–7 | date = September 2005 | pmid = 16166284 | doi = 10.1158/0008-5472.CAN-04-1198 | doi-access = free }}</ref>

Point mutations may arise from spontaneous mutations that occur during DNA replication. The rate of mutation may be increased by mutagens. Mutagens can be physical, such as radiation from [[ultraviolet light|UV rays]], [[X-ray]]s or extreme heat, or chemical (molecules that misplace base pairs or disrupt the helical shape of DNA). Mutagens associated with cancers are often studied to learn about cancer and its prevention.