Human DNA replication: fiber autoradiographic analysis of diploid cells from normal adults and from Fanconi's anemia and ataxia telangiectasia.

Fiber autoradiograms prepared from radioactive DNA of diploid skin fibroblasts and lymphocytes from normal adult humans show patterns of replication of chromosomal DNA that are closely similar to those from other mammalian cells. The rate of replication fork movement is 0.64 micrometer/min and 0.42 micrometer/min for fibroblasts and lymphocytes respectively. In both types of cells, replication units show a median length of about 70 micrometer. Replication proceeds bidirectionally from a central origin in most units and adjacents units initiate synthesis synchronously. In skin fibroblasts from individuals with Fanconi's anemia or ataxia telangiectasia, the autoradiographic patterns of DNA replication are the same as in controls. This suggests that S phase DNA synthesis is normal in these disorders.