[Effect of mitomycin C (MMC) on the fusion points of reciprocal translocations].

Lymphocytes from five patients having a reciprocal translocation were exposed to MMC to test the stability of the point of reunion which was localized in an euchromatic region. The results showed that the point of fusion in this type of translocations in not a preferential breakpoint. In a patient carrier of a (1;7) translocation, the derivate chromosome showed a significant increased number of breaks compared with the homologous chromosomes. No explanation is available for this finding. Our results support the hypothesis that the observed dissociation of Robertsonian translocation is related to the fact that the point of reunion is located in a heterochromatic region.