X-chromosome inversion in Drosophila melanogaster accompanied by a mosaic-type position effect: an analysis using cloned DNA fragments

DNA fragments carrying the genes affected by position effect variegation in the In(1LR)pn2a chromosome were revealed. In situ hybridizations demonstrate preservation of specific DNA sequences in the polytene chromosome regions containing the inactivated genes. It was shown that both euchromatic-heterochromatic boundaries in the In(1LR)pn2a chromosome contain the mobile element B104 (roo).