Nature of chromosome gaps induced by alkylating agents and γ-rays as revealed by caffeine treatment

In the cells of primary roots of Crepis capillaris, post-treatment with caffeine increased the frequency of gaps and chromosomal aberrations induced by the alkylating agents ethyleneimine and N-nitroso-N-methylurethane and γ-rays. The increase in the frequency of gaps was considerably lower than that observed in chromosomal aberrations, this being more strongly expressed in the case of the alkylating agents. The potentiating effect of caffeine on the γ-ray-induced chromosomal gaps was a little higher in S as compared with G₂. These results lead to the conclusion that the alkylating agents and the γ-rays might induce 2 types of chromosomal gap.