Folic acid sensitive fragile sites are not limited to the human karyotype. Demonstration of nonrandom gaps and breaks in the Persian vole Ellobius lutescens Th. inducible by methotrexate, fluorodeoxyuridine, and aphidicolin.

At least four folic acid sensitive fragile sites have been detected in the karyotype of the Persian vole Ellobius lutescens Th. (Rodentia, Microtinae). Two such "hot spots" are located on chromosome 1 flanking the pericentric segment which is inverted in many individuals. The fragile site on 1p was observed on both homologues in one cell. Our findings suggest that fragile sites are common properties of mammalian chromatin and might have played a role in karyotype evolution.