Abstract
In the previous paper the author reported that the male of reverted wild strain, which was obtained by the reverse mutation of short arista mutant and selected more than several generations, has peculiar Y chromosome of the following nature.
When a reverted wild male is crossed to short arista, or Delta, both on the III chromosome, sa or D behave as if they are sex-linked. When an Abrupt (sex-linked) female is crossed to a reverted wild male, the Ab character segregates as if it is an autosomal mutant. Furthermore when a female which has a lethal of semi-lethal factor on the one of her X chromosome is crossed with this reverted wild male, the effect of the lethal or semi-lethal factor on her X chromosome is suppressed. These unusual phenomena are explained on the basis of the presence of a peculiar Y chromosome in the reverted wild male. The author's hypothesis is as follows: 1. The Y chromosome in this species has a strong male determining factor, 2. A translocation between the Y and the III chromosome gave rise to a third chromosome with a part of Y containing the male determining gene; Thus, the reverted wild male has such a III-Y chromosome instead of a normal Y chromosome.
Furthermore, the author obtained recently two spontaneous recessive mutants, coarse and brown, which are both on the third chromosome. The result of genetic studies of these mutants indicates that the genes for these mutants are locate on the portion of the III chromosome which is homologous to that which is translocated to the Y chromosome described above. Crossing over takes place between the two. Crossing over also takes place between the III chromosome with D and the Y chromosome with translocation from the III chromosome, thus giving rise to a III-Y chromosome with D gene. The crossing over between X with Ab and normal Y chromosome occurs also. These crossing overs have occurred frequently in males.
