An Abnormal Staining Capacity of the Sixth Salivary Gland Chromosome of a Strain of Drosophila virilis

Abstract

1. The sixth salivary gland chromosome of the New Orleans strain of D. virilis has a markedly lower staining capacity than that of other strains.
2. This chromosome is also wider and longer than those in other strains. The arrangements of the bands, however, show no difference when crossed, a complete somatic synapsis occurs between this chromosome and the corresponding chromosome of any other strains in the heterozygous condition.
3. Among 23 strains from various localities of Japan and China, as well as of America examined, none had a sixth chromosome like that of the New Orleans. Only a mutant stock, Gap² hump/lethal 6a derived from the American Gap² stock, contained such a chromosome.
4. No difference was found in the frequency of crossing over between the sixth chromosomes of the New Orleans and that of other strains.
5. In a new composite chromosome derived from such crossing over, the distal half from VI1A to VI1G is made up of the New Orleans chromosome and the other half of a section, VI1F to the proximal end, of a normal chromosome. This gives another case of cytological demonstration of the phenomenon of crossing over.
6. A new allelomorph of Gap¹¹ was discovered in the New Orleans stock.
7. No significant difference in genetical behaviour exists between the New Orleans and normal strains. Nevertheless the markedly low viability and fertility of the stock with the recombination sixth chromosome is possibly due to some incompatibility between the two kinds of chromosomes.