Early- and late-replicating deoxyribonucleic acid complexes in HeLa nuclei.

Abstract The DNA which replicated early in the period of DNA synthesis in synchronized cultures of HeLa cells was labeled with [ 3 H]thymidine. After several generations of random growth the cells were resynchronized and exposed to bromodeoxyuridine for various portions of the DNA-synthesis period. The 3 H label was carried in the bromodeoxyuridine-containing, heavy hybrid of the DNA that replicated early in the second synchronized cell cycle.