Pre-implantation embryos of Chinese hamster. II incidence and type of karyotype anomalies after treatment of the paternal post-meiotic germ cells with an alkylating mutagen.

Ninety-two male Chinese hamsters were treated with a single, sub-lethal dose of the alkylating cytostatic drug Trenimon. After 3--23 days they were mated with untreated females. The great majority of the male germ cells had been exposed to the mutagen while they were in the highly sensitive post-meiotic spermatid stage. The karyotypes of the resulting embryos were studied in the 4--8-cell stage. Out of 221 analysable embryos, 24.4% had aberrant karyotypes. Ploidy and genome mutations were, at 0.9% each, within control limits. Structural aberrations, involving one or several chromosomes, were present in 23.6% of the embryos (control 1.8%). 51% had a single aberrant centric element. The most frequent aberration types were deletions (54%), dicentrics (16%), translocations inversions and complex rearrangements with 22% and rings with 7%. About one-third of the cells, in addition, contained acentric fragments.