Editing Frameshift mutation (section)

===Genetic or environmental===

{{Main article|Mutation}}

This is a genetic mutation at the level of nucleotide bases. Why and how frameshift mutations occur are continually being sought after. An environmental study, specifically the production of [[UV]]-induced frameshift mutations by DNA polymerases deficient in 3′ → 5′ exonuclease activity was done. The normal sequence 5′ GTC GTT TTA CAA 3′ was changed to GTC GTT T TTA CAA (MIDT) of GTC GTT C TTA CAA (MIDC) to study frameshifts. [[E. coli]] pol I Kf and T7 DNA polymerase mutant [[enzymes]] devoid of 3′ → 5′ exonuclease activity produce UV-induced revertants at higher frequency than did their [[exonuclease]] proficient counterparts. The data indicates that loss of proofreading activity increases the frequency of UV-induced frameshifts.<ref>{{cite journal|last=Sagher|first=Daphna|author2=Turkington, Edith|author3= Acharya, Sonia|author4= Strauss, Bernard|title=Production of UV-induced Frameshift Mutations in Vitro by DNA Polymerases Deficient in 3′ → 5′ Exonuclease Activity|journal=Journal of Molecular Biology|volume=240|issue=3|pages=226–242|doi=10.1006/jmbi.1994.1437 |pmid=8028006|date=July 1994}}</ref>