Chemical differentiation with fluorescent alkylating agents in Vicia faba metaphase chromosomes

Abstract With the purpose of searching for chemical bases for the transfer of differentiation information through metaphase, efforts have been made cytochemically to identify chemical and physiochemical differences between different parts of metaphase chromatin in Vicia . Equipment has been developed for very high resolution quantitative spectrophotometric determinations on chromosomes and for fluorimetric work with low irradiation load on the object. A bifunctional highly fluorescent quinacrine mustard was shown to give chromosome breaks preferentially localized to heterochromatic chromosome regions (identifiable by cold treatment) in the M-chromosome. This and other fluorescent mustards of different types accumulated preferentially in the same regions, which then appear as strongly fluorescent bands. In these bands the fluorescence per unit DNA is higher than in the rest of the chromosome. Possible mechanisms for the fluorochrome-binding are discussed.