title: Replication of the genes coding for 5 S RNA in synchronized HeLa cells.
abstract: The duplication of the genes coding for 5-S RNA has been followed during the S phase of HeLa cell cultures synchronized by mitotic detechment. Replication was analyzed by exposing the cultures to bromodeoxyuridine (BrdUrd) for 3 h at successive intervals and analyzing the DNA product in CsCl density gradients. DNA containing the 5-S genes was detected in the gradients by molecular hybridization using purified 125I-labeled 5 S RNA. In addition, as an internal marker of S phase chronology, late DNA replication was followed by examining the incorporation of [3H]thymidine into repetitive DNA (C0t less than 0.01 fraction). The results indicated that greater than 85% of the cells in the culture were synchronously dividing and that greater than 80% of the 5-S genes replicate in the first half of S phase, whereas the rapidly reassociating fraction of the DNA replicates in the second half of S phase.
mesh_terms: D000225:Adenine / Q000378:metabolism; D001973:Bromodeoxyuridine / Q000378:metabolism; D002453:Cell Cycle; D004247:DNA / Q000096:biosynthesis; D004261:DNA Replication; D005796:Genes; D006367:HeLa Cells / Q000378:metabolism; D009693:Nucleic Acid Hybridization; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D013936:Thymidine / Q000378:metabolism; D014529:Uridine / Q000378:metabolism
chemical_list: D012335:RNA, Ribosomal; D004247:DNA; D001973:Bromodeoxyuridine; D000225:Adenine; D013936:Thymidine; D014529:Uridine