ELECTRON-MICROSCOPY OF CHROMOSOME ORGANIZATIONAL-STRUCTURE CHANGES DUE TO FORMAMIDE

The structure of isolated human metaphase chromosomes treated with a s olution containing 0-70% formamide and spread over a protein monolayer , was studied by an electron microscope. When the formamide concentrat ion was increased, the chromosomes gradually decondensed and the scaff old structure was more sharply expressed, whereas the chromatin fibril loops coming from the central part of the chromosome, lost nucleosoma l structure. Polyacrylamide gel electrophoresis of proteins after form amide treatment showed that the major part of the histones remained in the chromosome composition, although, the morphology of the chromosom es treated in 70% formamide resembled the structure of expanded deprot einized chromosome preparations that were described in the literature.