Mitotic gene conversion induced in yeast by isoniazid. influence of a transition metal and of the physiological conditions of the cells.

Isoniazid (INH) induced mitotic gene conversion at the trp5 locus of strain D7 of Saccharomyces cerevisiae. A suggested mechanism involving autoxidation of INH and production of hydrogen peroxide is supported by the facts that (i) the presence of a transition metal, Mn(II), greatly enhanced the effect of INH, (ii) cells stored for a long time in the refrigerator are much more sensitive to INH + Mn(II) than fresh cells probably due to loss of catalase and/or peroxidase activity, (iii) presence of S9 mix during the treatment eliminated the effect of INH + Mn(II).