The DNA of three previously cloned interband regions (85D9/D10, 86B4/86, an
d 61C7/C8) of Drosophila melanogaster polytene chromosomes has been tested
for the presence of matrix association regions (MAR), using the in vitro ma
trix-binding assay of Cockerill and Garrard. MARs were found in all three i
nterband regions under study. These results are discussed in frames of a mo
del postulating that interband regions of polytene chromosomes correspond t
o the chromosomal DNA loop borders, which can be identified in interphase n
uclei using biochemical approaches. (C) 1999 Wiley-Liss, Inc.