THE MODIFICATION OF REPRODUCTION IN INSECTS TREATED WITH ALKYLATING AGENTS. II. DIFFERENTIAL SENSITIVITY OF OOCYTE MEIOTIC STAGES TO THE INDUCTION OF DOMINANT LETHALS

¹ Entomology Research Division, Agric. Res. Serv., U.S.D.A., Kerrville, Texas

When adult females of the screw-worm fly, Cochliomyia hominivorax, are topically treated with alkylating agents, dominant lethal mutations are induced in the oocytes. Since the meiotic stage of the oocytes is correlated with the age of the female, it is possible to treat oocytes in either early prophase, metaphase, or anaphase of the first meiotic division. When such treatment is made, fewer dominant lethals are induced in prophase oocytes than in oocytes in the other two stages. This trend was consistently found in studies with three chemical mutagens: (a) tretamine (2,4,6,-tris(1-aziridinyl)-s-triazine), (b) a benzoquinone derivative (2,5,-bis(1-aziridinyl)-3,6,-bis(2-methoxyethoxy)-p-benzoquinone), and (c) thiotepa(tris(1-aziridinyl) phosphine sulfide). In addition to demonstrating the differential sensitivity of various oocyte meiotic stages to these agents, this report compares the mutagenic efficiency of the agents and discusses the possible basis for differential sensitivity of cell stages to mutagens.