Bloom's syndrome: DNA replication in cultured fibroblasts and lymphocytes.

Analysis of DNA fiber autoradiograms from Bloom's syndrome skin fibroblasts and blood lymphocytes shows a retarded rate of replication fork movement compared to normal adult controls. Other measurements from the autoradiograms--replication unit length, incidence of bidirectional replication, and degree of initiation synchrony--are normal in Bloom's syndrome cells. These results suggest that a slow rate of fork movement is a specific manifestation of defective DNA synthesis in all Bloom's syndrome cells.