¶ … Color Discrimination in carriers of color deficiency Hood, S.M., Mollon, J.D., Purves, L., Jordan, G. (2006) Color discrimination in carriers of color deficiency. Vision Research 46: 2894-2900 is an article on chromatic discrimination in carriers of the X-inactivated chromosome. The investigators examine the recurrent claim that discrimination is impaired in some carriers of color deficiency and argue that carriers of deficiencies of the long-wave-sensitive cones (protan carriers) must be considered separately from carriers of deficiencies of the middle-wave-sensitive cones (deutan carriers). The authors cite references to indicate that the photopigments of the long-wave-sensitive (L) cones and the middle-wave-sensitive (M) cones are encoded by a small array of genes on the q arm of the X-chromosome.

According to Hood et al., to understand why a difference between...

And M. cones in the retina of a female subject. First, random X-chromosome inactivation determines which X-chromosome will be expressed in a given cone cell A second stochastic event later determines which type of photopigment gene (L or M) is actually expressed by the favored X-chromosome: this latter event is thought to be the probabilistic binding of an upstream locus control region to the promoter region of one of the genes in the array. From this arise differences in the ratios in L. And M. cones between protan and deutan carriers. This led the authors to hypothesize that there are differences in red-green color discrimination between protan and deutan carriers.
They used the MacLeod -- Boynton chromaticity diagram on normal male…