Color blindness
Genetic testing

While genetic testing cannot directly evaluate a subject's color vision (phenotype), most congenital color vision deficiencies are well-correlated with genotype. Therefore, the genotype can be directly evaluated and used to predict the phenotype. This is especially useful for progressive forms that do not have a strongly color deficient phenotype at a young age. However, it can also be used to sequence the L- and M-Opsins on the X-chromosome, since the most common alleles of these two genes are known and have even been related to exact spectral sensitivities and peak wavelengths. A subject's color vision can therefore be classified through genetic testing, but this is just a prediction of the phenotype, since color vision can be affected by countless non-genetic factors such as your cone mosaic.
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