Studies on chemical induction of chromosomal aberrations in postcopulation germ cells and zygotes of female mice. I. Comparative studies on the frequency of first-cleavage chromosomal aberrations and dominant-lethal mutations.

Abstract

The correlation between dominant-lethal mutations and chromosome aberrations in first cleavage and the relative sensitivities of germ cells and zygotes to the induction of chromosome aberrations by methyl methanesulfonate (MMS), iso-propyl methanesulfonate (iPMS) and Mitomycin C (MC) were studied in copulated females. All chemicals tested induced dose-dependent dominant-lethal erects. The incidence of dominant lethals induced by postcopulation treatment with MMS was about half of that induced in spermatozoa and late spermatids in males at same dose, whereas the incidence obtained by iPMS or MC treatment was about 7 and 14 times, respectively. The relationship between dominant lethals and chromosome aberrations at first cleavage was not necessarily direct, which was suggestive of the involvement of some non-genetic erects. Chromosome aberrations observed in first cleavage were very high in preovulatory oocytes and sperm in oviducts (immediately after copulation) by MMS or MC treatment. iPMS, on the other hand, did not induce so many aberrations as MMS or MC did. In the case of MMS, the number of structural aberrations in the paternal chromosomes was greater than in maternals, but the extent of aberrations induced by MC or iPMS could not be distinguished because of the chemical-induced delay of pronuclei to develop.