STUDIES ON MICRONUCLEI INDUCED BY MITOMYCIN-C IN ROOT CELLS OF VICIA FABA

Mitomycin-C produces localised chromosome breaks in heterochromatic segments of Vicia root cells. These acentric fragments and lagging chromosomes form micronuclei. About 20% of micronucleate cells can be induced either by exposing the roots to 1 μg/ml concentration of mitomycin for a period of 50-96 h or by 5 μg/ml concentration for 5 h and then recovering the cells for 2 to 3 days. The number of micronuclei per cell was variable but the majority of the cells (about 86%) contained only one micronucleus. Exposure of roots containing micronucleate cells to labelled precursors revealed that many of the micronuclei can synthesise DNA, RNA and proteins. This synthetic ability of micronuclei was dependent on their size and the presence of nucleolar material. In comparison to radiation the mitomycin-induced micronuclei have longer viability. This difference was due to higher amount of heterochromatin and ribosomes present in micronuclei induced by mitomycin. © 1969.