CORRELATION BETWEEN SITES OF DNA LOOPS ANCHORAGE TO NUCLEAR MATRIX, MATRIX ASSOCIATION REGIONS, AND AUTONOMOUSLY REPLICATING SEQUENCES IN AN EXTENDED REGION OF THE DROSOPHILA-MELANOGASTER X-CHROMOSOME

The recently developed procedure of chromosomal DNA loop excision by t opoisomerase II-mediated DNA cleavage at matrix attachment sites has b een applied for investigating the domain structure of the 14B/15B-regi on of Drosophila melanogaster X chromosome. Eleven anchorage sites wer e mapped within the 500-kb region. Ten of these anchorage sites coloca lized with the previously mapped matrix association regions (MARs). Ho wever, the majority of these MARs proved to bear no relation to DNA lo op anchorage to nuclear matrix in the cell type studied.