Abstract
This lecture* is a comprehensive summary of all the genetic studies concerned with Drosophila ananassae carried out by the writer and his co-workers since 1931 when the flies were found by chance in Tokyo. It was presented under three major headings, (a) mutants and gene analysis, (b) experimental studies, and (c) studies on population genetics.
Genetic characteristics of this species are as follows:
(1) The fourth chromosome is considered to correspond to the dot chromosome of D. melanogaster or other species of the same group, composed of a bit of euchromatin and a large proportion of heterochromatin, the latter of which occupies major part of the V-shaped body. Further, it is partly identical to some parts of X- and Y-chromosomes, causing such a special allelism of bobbed locus that +bb in Y is allelic with bb in IV and not in X.
(2) In both the second and third chromosomes, except a few dominant genes, all other mutants found belong to the left arms of the chromosomes. The interpretation that the mutability of genes differs in the two arms is preferable.
(3) Power to enhance crossing over was found in the right arm of the second chromosome. The enhancer is able not only to increase the female crossing over somewhat, but also to induce male crossing over. The same kind of enhancer has been known in the third chromosome too.
It is added that this species is a cosmopolitan and domestic species and that the flies frequently carry various types of chromosomal rearrangements in the natural population.
