A G protein
If a patient lacks the gene for transducin, their photoreceptor cells in the retina would not be able to function properly. Transducin is a crucial protein involved in the visual signaling pathway, allowing the conversion of light stimuli into electrical signals that the brain can interpret. Without transducin, the patient would likely experience vision problems or even blindness.
Axons carrying impulses from the retina are bundled together at the posterior aspect of the eyeball and issue rfom the back of the eye as the optic nerve. At the optic chiasma, the fibers from the medial side of each eye cross over to the opposite side of the brain; the fiber tracts that result are the optic tracts. The optic tract fibers synapse with neurons in the thalamus, whose axons form the optic radiation, which runs to the optic cortex located in the occipital lobe of the brain
Rhodopsin is an organic compound called a Visual Pigment. The absorption of lights by visual pigments is the crucial first step in the process of photoreception. In the presence of light, the protein opsin is activated allowing retinal to bind to its active site (retinal synthesized with vitamin A). The retinal and opsin protein complex is thus known as rhodopsin. When the pigment absorbs a photon, the shape of the protein changes shape and bleaching separation occurs. Retinal must be restored in presence of ATP and Opsin must be reactivated in order for the cycle to repeat (this typically takes 30 minutes).