THE INFLUENCE OF INHIBITORS OF DNA-SYNTHE SIS OF INDUCED MUTAGENESIS

The mutagenic effect induced by mitomycin C (MC) 20 mg/ml in early, mi ddle and late G1-phase of Crepis capillaris seeds was modified by DNA synthesis inhibitors - caffeine 5 mM, hydroxyures (HU) 5.10(-3) M, 1-b eta-D-arabinofuranosylcytosine (araC) 1.10(-3) M and aphidicolin (APC) 0,5 mg/ml in the DNA postsynthesis phase (G2). It was shown that unde r the action of MC in early G1 and the inhibitors in the G2 the total number of aberrations for fixations is lower in all the cases than und er the action of MC only. The action of MC in the middle phase results in the differential effect of the inhibitors. HU and APC were shown t o potentiate the effect induced by MC and ara-C to reduce it. In both cases, caffein at the dose 5 mM had small effect on DNA damages induce d by MC in early and middle G1. Under the action of caffeine and HU in the G2-phase the crosslinks induced by MC in the late G1 result in ab errations of chromosomal type, illegal for the S-dependent mutagenesis . On the whole, the process of mutation formation turned out to be sen sibilized. The specificity of mutgenesis under the action of MC sugges ts the appearance of mutations of the chromosomal type after the DNA s ynthess in G2 phase.