BASE-LINE AND MITOMYCIN-C (MMC)-INDUCED SISTER-CHROMATID EXCHANGES INXX AND XY CELLS OF CALLITHRIX-JACCHUS CHIMERIC TWINS

Lymphocytes from chimeric individuals of the species Callithrix jacchu s (Primates) were examined to evaluate differences in the frequency of sister chromatid exchanges (SCE) between XX and XY cells. The aim was to discover whether SCE differ according to genetic sex and whether X X and XY cells show a different sensitivity to SCE inducing agents. Th is experimental model has enabled us to eliminate the possible differe nces caused by environmental factors. The results obtained do not reve al significant differences between male and female cells, in either th e baseline SCE frequency or that induced by mitomycin C at concentrati ons of 0.01 and 0.03 mu g/ml. No significant differences were observed in the distribution of high SCE frequency cells (HFC), even if it is possible to observe a higher level of exchanges in XX cells in each tr ial. With regard to the phenotypic sex, there appears to be a trend to wards slightly higher SCE rates in females, even if results are not st atistically significant.