ABSTRACT
Differential banding patterns of chromosomes, usually observed at specific regions on particular levels, were initially developed for the analysis of human chromosome segments. These bands are made visible through low and high intensity regions under the fluorescence microscope or as differentially stained areas under the light microscope. The methods were then extended first to different animals and later to plant chromosomes. The different banding patterns have been employed in locating marker segments of chromosomes, particularly those with repetitive DNA sequences, in plant and animal systems. With quinacrine mustard, the fluorescent amino-acridine nucleus becomes intercalated within the double helix of DNA. The basic nitrogen atoms form ionic bonds with DNA phosphate and the alkylating side group binds covalently with guanine from DNA. The fact that both AT and GC specific fluorochromes are available and that sequential fluorescent staining of chromosomes and counterstaining with non-flurescent DNA ligands is feasible, means that suitable combinations may facilitate analysis of molecular mechanism.
