Distribution of mobile dispersed genes (mdg-1 and mdg-3) in the chromosomes of Drosophila melanogaster

The localization of mobile dispersed genes (mdg-1 and mdg-3) was studied by in situ hybridization with the polytene chromosomes of 20 laboratory stocks of Drosophila melanogaster. The average number of sites was 20 for mdg-1 and 12 for mdg-3, but the actual number varied from stock to stock (14–27 for mdg-1 and 5–18 for mdg-3). A total of 182 possible sites have been detected for mdg-1 and 123 sites for mdg-3. In spite of the individual and interstock variation, the distribution over chromosomes was found to be nonrandom for mdg-3 and especially for mdg-1. Frequently occurring sites of mdg-1 hybridization were revealed, most of which coincided with regions of intercalary heterochromatin, especially in chromosome 2.