Genetical studies on the non-molting dwarf” mutation in Bombyx mori

The recessive lethal mutation “non-molting dwarf” (symbol, nm-d) was found in F₂progenies of the cross between a female sparsely mottled with fine translucent dots and a normal male. Linkage test showed that the nm-d gene was linked to Dominant chocolate (I-a) which had been mapped at position 5.9 on the ninth linkage group. Precise localization of nm-d was performed by a three-point experiment of the type I I-a/nm-d sib-mating. The locus of I (Yellow inhibitor) gene on the genetic map corresponds to position 0.0. The recombination value between I and nm-d was calculated to be 0.13%, nm-d and I-a 6.60%, I and I-a 6.74%, respectively, through the observation of 10,895 individuals. Hence the arrangement of these three gene loci on the chromosome is in the order of I/nm-d-I-a, and nm-d gene lies at position 0.1 on the ninth linkage group.