Inheritance of albinism in the medaka, Oryzias latipes, with special reference to gene interaction.
Genetics 1969 62:797-809.
Albionos (pink eyed) of the medaka (Oryzias latipes) appeared for the first time from a non pedifreed stock, and were mated with other color varieties (brown, blue, orange-red and white). Albinism (i) is found to be an autosomal gene ressesive to its normal allele (+i). It is non allelic with all heretofore known color genes including the be series alleles (B, B', b) controlling melanin formation, and is semilethal. When an original albino fish (ib) is crossed with wild type (+iB), the segregation ratio in the F2 advanced embryos is 9 : 3: 4 for +iB, +ib and and albinos (iB and ib) characteristic for two genes interacting by recessive epistasis. By test crosses of F2 adult albinos, B-carying and b-carrying albinos are actually detected. The albino gene manifests pleiotropic effects. When homozygous, it not only inhibits melanin formation but partially suppresses xanthine pigmentation governed by the sex-linked R and Rd genes. For the expression of the characteristic colors of varieties, the presence of the normal allele (+i) of i is indispensible. If i is homozygous, all color patterns of other varieties do not appear and all medakas turn out to be albino even though they are carrying various color genes. For the ordinary color (brown) of the wild type to appear, at least a dozen normal alleles of recessive color genes are necessary. Of these, +i is the most essential.