Dynamics of appearance of locus and suppressor revertants in adenine auxotrophic yeasts incubated on selective medium

When auxotrophic cells grown on medium containing the limiting metabolite and transferred to selective medium without this metabolite, the process of appearance of preexisting revertants may last 6-8 days, with the locus revertants appearing more coordinatedly and in shorter time, than the suppressors. Account of both types of revertants is complicated by the occurring of new reversions due to residual growth. The most correct methodics for accounting is: smearing the newly transferred to the selective medium colonies by a glass spatula and counting multiple revertants. This method significantly enhances detectability of preexisting revertants, which usually sharply decreases with increasing the number of cells in the primary colonies above 5x105. 6 refs.; 7 figs.; 2 tabs