Sevenless

{{Short description|Gene in Drosophila eye development}}

{{Infobox nonhuman protein |UniProt=P13368|Organism=Drosophila melanogaster |Name=Sevenless|Symbol=sev}}

Sevenless (sev) is a gene in the fruit fly Drosophila melanogaster that encodes a receptor tyrosine kinase protein essential to the development of the R7 photoreceptor cells in the Drosophila embryonic eye.{{cite journal|url=https://www.ncbi.nlm.nih.gov/books/NBK21720/|title=Receptor Tyrosine Kinases and Ras| vauthors = Darnell J, Baltimore D, Matsudaira P, Zipursky SL ,Berk A, Lodish H |date=10 June 2019|journal=Molecular Cell Biology. 4th Edition|via=www.ncbi.nlm.nih.gov}} The Drosophila ommatidium contains 8 distinct retinula or R cells, each of which has a different spectral sensitivity. The R7 photo receptor, located in each of several ommatidia in the fly's compound eye, is used to detect ultraviolet light.{{cite book | vauthors = Smith CU |title= Elements of Molecular Neurobiology|url=http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471560383.html |year=2002 |orig-year= 1989|publisher= Oxford Journals|isbn= 0-471-56038-3|pages= 450–451|chapter=19.5 Morphogenesis in the Drosophila eye |chapter-url=https://books.google.com/books?id=-pHZsSXDcesC&dq=retinula+sevenless&pg=PA451 }} The R8 photoreceptor contains an activator of the RTK (receptor tyrosine kinase) for on a precursor R7 cell, called the bride of sevenless (BOSS). The binding of BOSS to sevenless stimulates a complex series of reactions involving the RTK (sevenless), MAP kinases, Ras and many more molecules to differentiate that precursor R7 photo receptor to a fully functional R7 photo receptor that can see UV light. Much of this knowledge was gained by examining flies with a mutant sevenless which still produced a fully functional R7 photoreceptor when a dominant Ras was injected into the mutant R7 precursor.