On the Chemical Basis of Chromosome Banding Patterns

Abstract

A comparative study of the staining characteristics of four reagents for human chromosomes has been carried out. The four reagents are: (I) quinacrine mustard, as an alkylating agent, (II) the dihydrory derivative of quinacrine mustard, (III) quinacrine, and (IV) 9-amino-6-chloro-2-methoryacridine. The last reagent does not possess the amino substituted side chain even though it has the same intercalating nucleus. Comparison of the first three compounds in their staining and banding behavior suggested the initial step leading to banding may be the displacement of the nucleoprotein sites in chromosomes. The Q and G banding could he blocked experimentally by treating the chromosome preparation with dimethylamine solution. This result may suggest that these sites have weaker basic proteins (nonhistone proteins?). The use of compound IV, which does not have the side chain in the molecuk but docs have the same intercalating chromophore, did not lead to handing and gives indirect support to this hypothesis. A combined use of compound IV and quinacrine may be useful for the determination of total DNA vs. banding DNA.