Aberration induction by mitomycin C in early primary spermatocytes of mice.

MC is well known to induce dominant lethal mutations in mouse spermatocytes. Tests were done to determine whether chromosomal aberrations could be identified in spermatocytes as being responsible for the dominant lethal effects. Male mice were treated with single doses of MC during DNA synthesis preceding meiosis and during early prophase of meiosis. Simultaneous labeling was performed to identify cells that were in S-phase during the time of treatment. Diakineses-metaphases I were analyzed for the occurrence of univalents, gaps, fragments and rearrangements. The frequencies of cells with aberrations increased with dose and time after treatment. Maximal values were obtained after 12 days, indicating that MC was most effective in cells undergoing DNA replication. 95% of these cells were labeled. The majority of aberrant cells contained one or more fragments. These cells will lead to dominant lethality of the zygotes after fertilization. Cells with rearrangements occurred 11 and 12 days after treatment. These cells can develop into sperm carrying a reciprocal translocation which would then give rise to semi-sterile progeny after fertilization. Further investigations are needed to study the transmission of rearrangements observed in primary spermatocytes.