Abstract
Photooxidation is believed to preferentially remove guanine (G) residues from chromosomal DNA. G interspersion, moreover, has been hypothesized as quenching quinacrine (Q) fluorescence in cytological preparations. Hence, we used photooxidation as a tool for inducing possible changes in the Q-banding pattern of Drosophila melanogaster, Drosophila virilis, and Mus musculus metaphase chromosomes. An enhanced Q fluorescence, which was particularly evident in certain chromosomal regions, was found. This finding would support the postulated primary role of G in determining Q bands in eukaryotic chromosomes.