Genetic studies of variation in Rayleigh and photometric matches in normal trichromats

The inheritance of Rayleigh match midpoints and photometric matches (551-667 nm) was studied in observers with normal color vision. An analysis was performed to evaluate whether the measured interobserver variations in these two traits were consistent with single gene allelic variation, polygenic variation, or environmental factors. A bipartite 2 deg field and a computerized tracking method were used to obtain Rayleigh matches; a new photometric technique, termed heterochromatic modulation photometry (HMP), was used to obtain photometric matches. Data were collected from 72 nonrelated males to determine distribution characteristics for the normal population. The distributions were analyzed for evidence of multimodality and the results indicated that the distributions for Rayleigh match midpoints and HMP matches obtained in this study were unimodal and symmetrical. Data from 52 observers from 5 families were used to study the transmission of the two traits in pedigrees. Statistical analysis of the pedigree data suggested that the major source of variations for Rayleigh match midpoints and for HMP matches were each due to allelic variation at single gene loci; that is, each may be determined by a single gene. Results were inconclusive as to whether variation in the two traits could be determined by the same gene.