Editing DDT (section)

===Mechanism of insecticide action===
In insects, DDT opens [[voltage-sensitive sodium channel|voltage-sensitive sodium ion channels]] in [[neuron]]s, causing them to fire spontaneously, which leads to spasms and eventual death.<ref name=":1">{{Cite journal|last=Dong|first=Ke|date=2007-01-06|title=Insect sodium channels and insecticide resistance|journal=Invertebrate Neuroscience |volume=7|issue=1|pages=17–30|doi=10.1007/s10158-006-0036-9|issn=1354-2516|pmc=3052376|pmid=17206406}}</ref> Insects with certain [[mutation]]s in their sodium channel [[gene]] are [[insecticide resistance|resistant]] to DDT and similar insecticides.<ref name=":1" /> DDT resistance is also conferred by up-regulation of genes expressing [[cytochrome P450]] in some insect species,<ref>{{cite journal | vauthors = Denholm I, Devine GJ, Williamson MS | title = Insecticide resistance on the move | journal = Science | volume = 297 | issue = 5590 | pages = 2222–2223 | date = September 2002 | pmid = 12351778 | doi = 10.1126/science.1077266 | s2cid = 83741532}}</ref> as greater quantities of some enzymes of this group accelerate the toxin's metabolism into inactive metabolites. Genomic studies in the model genetic organism ''[[Drosophila melanogaster]]'' revealed that high level DDT resistance is polygenic, involving multiple resistance mechanisms.<ref>{{cite journal | vauthors = Pedra JH, McIntyre LM, Scharf ME, Pittendrigh BR | title = Genome-wide transcription profile of field- and laboratory-selected dichlorodiphenyltrichloroethane (DDT)-resistant ''Drosophila'' | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 101 | issue = 18 | pages = 7034–7039 | date = May 2004 | pmid = 15118106 | pmc = 406461 | doi = 10.1073/pnas.0400580101 | bibcode = 2004PNAS..101.7034P | doi-access = free }}</ref> In the absence of genetic adaptation, Roberts and Andre 1994 find [[avoidance response|behavioral avoidance]] nonetheless provides insects with some protection against DDT.<ref name="Bijlsma-Loeschcke-2011">{{cite journal | title=Genetic erosion impedes adaptive responses to stressful environments | last1=Bijlsma | first1=R. | last2=Loeschcke | first2=Volker | journal=[[Evolutionary Applications]] | publisher=[[Blackwell Publishing|Blackwell]] | issn=1752-4571 | date=7 November 2011 | volume=5 | issue=2 | pages=117–129 | doi=10.1111/j.1752-4571.2011.00214.x | pmid=25568035 | pmc=3353342 | s2cid=18877551}}</ref> The [[M918T]] mutation event produces dramatic ''[[knockdown resistance|kdr]]'' for [[pyrethroid]]s but Usherwood et al. 2005 find it is entirely ineffective against DDT.<ref name="Scott-2019">{{cite journal | last=Scott | first=Jeffrey G. | title=Life and Death at the Voltage-Sensitive Sodium Channel: Evolution in Response to Insecticide Use | journal=[[Annual Review of Entomology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=64 | issue=1 | date=2019-01-07 | issn=0066-4170 | doi=10.1146/annurev-ento-011118-112420 | pages=243–257| pmid=30629893 | s2cid=58667542 }}</ref> Scott 2019 believes this test in ''Drosophila'' [[oocyte]]s holds for oocytes in general.<ref name="Scott-2019" />