THE NATURE OF THE CHANGES EFFECTED IN CHROMOSOMAL MATERIALS BY THE CHELATING AGENT EDTA

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Abstract
Evidence is presented that the deformational changes effected in plant and animal chromosomes by EDTA are referable to alterations in the colloidal properties of structural nucleoproteins. Cytological studies of salivary-gland cells of Drosophila melanogaster indicated that 0.001 [image] EDTA causes marked swelling of nucleoli, with peripheral displacement of the laterally dispersed chromosomes. No evidence was obtained that 0.1, 0.01, or 0.001 [image] EDTA impairs the structural continuity of chromosomes by effecting their breakage or fragmentation. Cytochemical studies of salivary-gland cells and chemical analyses of onion-root-tip cells indicated that RNA is involved in the deformational changes. The findings lead to the conclusion that EDTA-induced chromosomal changes depend on modification of the general ionic environment of the cell and not merely on the selective removal of specific divalent cations from the fabric of the chromosomes. The implications of the findings with respect to theories of chromosome structure are discussed briefly.

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