Genetic effects of formaldehyde in yeast. I. Influence of the growth stages on killing and recombination.

In random cultures, stationary phase cells of Saccharomyces cerevisiae are more resistant to killing induced by formaldehyde than are exponentially growing cells. It is shown that this compound induces intra- and intergenic recombination in this eucaryotic organism. In synchronized populations the lag and G1 phases demonstrate the higher resistance to both killing and induction of recombinants by formaldehyde whereas maximal sensitivity occurs during the end of G2 and/or the mitotic division. This pattern in contrast with that found after treatments by ionizing or ultraviolet radiations.