Heredity of congenital deficiencies in color vision

The different varieties of congenital dyschromatopsias are inherited following different modes. The dyschromatopsias of the protan and deutan type, as well as the atypical achromatopsia (blue mono-cone monochromacy), are sex-linked recessive, the tritanopia probably autosomal dominant and the typical achromatopsia surely autosomal recessive. The mode of transmission of the tritanomalia is still dubious. Concerning the localisation of the genes on the X chromosome, the bilocular theory for the deutan and protan genes is accepted at the present time. These genes form a cluster with the genes of hemophilia A and G6PD deficiency. It is possible that this cluster is situated on the short arm of the X chromosome or on the long arm near the centromeric region. The exact situation will be known very soon, when the interpretation of the results of the cellular hybridisation, which are still discordant, will be well established.