Long - Range Polymerase Chain Reaction Method for Detection 3 of Human Red and Green Opsin Gene Polymorphisms

Human color-vision discriminates middlefrom long-wavelength spectral light 13 as a result of photopigment opsin genes found on the q-arm of the X-chromosome at 14 location Xq28. These so called ‘green’ and ‘red’ opsin gene sequences are 98% 15 homologous, producing middle-wavelength sensitive and long-wavelength sensitive 16 photopigment opsin gene sequences which differ by only seven locations at which 17 important amino-acid substitutions occur. Investigations of variations in green and red gene 18 arrays, and the consequences on phenotype expression, are the basis for color vision 19 anomalies, including those first described by Dalton in 1789 [1], and are important for 20 understanding expression mechanisms contributing to evolution of photopigment opsin 21 genotypes. Here we introduce a long-range polymerase chain reaction assay for specifying 22 the presence of genetic dimorphisms in human red and green gene sequences, and examine 23 the utility of the long-range PCR in predicting perceptual behaviors found in phenotypes 24 arising from identified genotypes. Consistent with behavioral differences correlated with 25 results from a short-range PCR genotyping method [2], the more specific long-range PCR 26 analysis indicates that dimorphisms commonly found in green and red opsin genotypes are 27 correlated with certain color perception behaviors. The long-range PCR presented provides 28 an additional tool for use in evaluating hypotheses about photopigment opsin gene 29 expression in color vision phenotypes. 30