What is the genetic cause for anomalous trichromacy?
Anomalous trichromacy, the most common type of colorblindness, is characterized by a shift in the sensitivity of one or more cone pigments. For reasons having to do with the genetic coding of color vision, these shifts overwhelmingly affect the L-cones and M-cones, and the shift is typically from the one toward the other. In other words, protanomaly makes the L-cone more like the M-cone, and deutanomaly makes the M-cone more like the L-cone. L- and M-cones distinguish between long and medium wavelengths. The L- and M-cone opsin genes lie adjacent to one another, head to tail, on an arm of the X-chromosome. The genes are responsible for the make-up of the cone opsin (protein). The cone opsin, along with retinal, makes up the pigment. Intragenic recombination between the L- and M-cone genes is common and can lead to the production of hybrid or fusion genes, some of which code for anomalous pigments. If there is variation in the L- and M-cone pigments, caused by a difference in their amin
