Fragile sites induced by 5-azacytidine and 5-azadeoxycytidine in the murine genome

The cytosine analogues 5-azacytidine and 5-azadeoxycytidine were used to induce fragile sites on mouse chromosomes. Sites of relative frequent fragility were ascertained and compared with fragile sites induced by the antimetabolites methotrexate, fluorodeoxyuridine and aphidicolin as reported previously. Considerable overlap of fragile sites induced by the very different agents is evident. Fragile sites are common to all chromosomes and most of them are susceptible to different modes of induction.