Editing Chronobiology (section)

===Melanopsin cells relay inputs from rods and cones===
[[File:Phototransduction and ipRGCs in mammals.jpg|thumb|alt=Phototransduction and ipRGCs in mammals|Light enters the eye and hits the retinal pigmented epithelium (maroon). This excites rods (grey) and cones (blue/red). These cells synapse onto bipolar cells (pink), which stimulate ipRGCs (green) and RGCs (orange). Both RGCs and ipRGCs transmit information to the brain through the optic nerve. Furthermore, light can directly stimulate the ipRGCs through its melanopsin photopigment. The ipRGCs uniquely project to the superchiasmatic nucleus, allowing the organism to entrain to light-dark cycles.]]
Hattar, armed with the knowledge that melanopsin was the photopigment responsible for the photosensitivity of ipRGCs, set out to study the exact role of the ipRGC in [[Photoentrainment (chronobiology)|photoentrainment]]. In 2008, Hattar and his research team transplanted [[diphtheria]] toxin [[genes]] into the [[mouse]] melanopsin gene locus to create [[mutation|mutant]] mice that lacked ipRGCs. The research team found that while the mutants had little difficulty identifying visual targets, they could not entrain to light-dark cycles.  These results led Hattar and his team to conclude that ipRGCs do not affect image-forming vision, but significantly affect non-image forming functions such as photoentrainment.<ref name="Fly in mammalian eye">{{cite web|last1=Graham|first1=Dustin|title=Melanopsin Ganglion Cells: A Bit of Fly in the Mammalian Eye|url=http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/elanopsin-ganglion-cells-a-bit-of-fly-in-the-mammalian-eye/|website=Webvision The Organization of the Retina and Visual System|publisher=University of Utah School of Medicine|accessdate=9 April 2015|url-status=dead|archiveurl=https://web.archive.org/web/20110427132440/http://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/elanopsin-ganglion-cells-a-bit-of-fly-in-the-mammalian-eye/|archivedate=27 April 2011}}</ref>