Z-DNA and the polytene chromosome

Indirect immunofluorescence shows that antibodies specific for the Z conformation of DNA bind to D. melanogaster polytene chromosomes in a specific and reproducible pattern. In our acetic-acid-fixed preparations, the binding is predominantly to interband regions, to puffs, and to some specific bands. As might be expected, the pattern of binding can be affected by cytological procedures. Bands and interbands show significant differences in their susceptibility to these procedures. Although further study is needed, our studies give no evidence that acetic acid treatment of intact cells is capable of causing conversion of B-form and Z-form DNAs. Instead, the experiments suggest that the Z conformation is preferentially available in interbands and a few other chromosome regions.