GENETIC VARIATIONS IN BASE-LINE AND ULTRAVIOLET LIGHT-INDUCED SISTER CHROMATID EXCHANGES IN PERITONEAL LYMPHOCYTES AMONG DIFFERENT MOUSE STRAINS

The variation in the induction of sister chromatid exchanges (SCEs) in the peritoneal lymphocytes of different mouse strains was investigated. For the baseline SCEs, BALB/c and outbred ICR showed the lowest frequency and DBA/2 and C57BL/6 the highest. BDF1 (C57BL/6 x DBA/2) was ranked among the highest,-while CDF1 (BALB/c x DBA/2) was intermediate between the parental strains. Regarding UV-induced SCEs, BALB/c was less susceptible as compared to DBA/2 and C57BL/6. Both BDF1 and CDF, showed values significantly higher than BALB/c, but not significantly different from DBA/2 or C57BL/6. ICR was ranked in the susceptible group. For the baseline SCEs of bone marrow cells, the overall ranking among strains was essentially the same as that for the baseline, but different from that for the UV-induced, SCEs in peritoneal lymphocytes. The present results can be explained by assuming that the major genetic factor contributing to the strain-dependent difference in the baseline SCEs is due to a codominant trait of a single allele, but that the UV-induced SCEs are complicated by other genetic factor(s).