SERINE ALANINE AMINO-ACID POLYMORPHISM OF THE L-CONE PHOTOPIGMENT ASSESSED BY DUAL RAYLEIGH-TYPE COLOR MATCHES/

The dual Rayleigh-type color match is the ratio of 621 nm light to 550 nm light that in admixture matches 586 nm light, divided by the ratio of 667 nm light to 550 nm light that in admixture matches 586 nm ligh t. Compared to the classical Rayleigh match, the dual-match procedure minimizes variation in color matching arising from differences in lens pigmentation and photopigment optical density, and thus amplifies ind ividual differences due to shifts in L Pigment lambda(max). We hypothe sized that the dual matches would provide a clearer distinction betwee n subjects with serine and subjects with alanine than would the classi cal Rayleigh match because individuals with serine express L pigments with a lambda(max) shifted toward longer wavelengths than do those wit h alanine. Classical Rayleigh color matches were compared with dual Ra yleigh-type color matches in 14 color-normal observers whose DNA had b een analyzed previously for the presence of the amino acid serine or a lanine at position 180 in the L opsin. The resulting distribution of d ual-match measurements for the seven subjects with serine does not ove rlap the distribution of measurements for the seven subjects with alan ine. The classical Rayleigh match measurements for these two groups of subjects, on the other hand, overlap substantially. More than half of the subjects' classical Rayleigh matches are within the overlapping r ange. The dual Rayleigh-type matches, therefore, provide an improved p sychophysical technique for assessing whether an individual observer h as serine or alanine at position 180.