title: DNA content and structure of (double) minutes of a methotrexate-resistant cell line.
abstract: We have determined the DNA content of intact double minutes (DMs) and of single minutes (SMs) by fluorometry of the individual chromatin bodies in metaphase spreads after staining with Feulgen-Schiff pararosaniline. We find that the intact DMs and SMs of the methotrexate-resistant mouse cell line 3T6R50 contain 4.4 megabase pairs (Mb) and 2.6 Mb DNA respectively, using the DNA content of E. coli (4.7 Mb) as a reference. As the pulsed field gradient gel electrophoresis experiments by van der Bliek et al. (1988) have indicated that the minutes of 3T6R50 cells contain a homogeneous population of 2.5 Mb DNA circles, we conclude that a SM contains one circular double strand DNA molecule of approximately 2.5 Mb, whereas DMs contain two.
authors.affiliation: Department of Molecular Biology, The Netherlands Cancer Institute, Amsterdam.
authors.forename: A P
authors.initials: AP
authors.lastname: Jongsma
authors.forename: W A
authors.initials: WA
authors.lastname: Duijndam
authors.forename: P
authors.initials: P
authors.lastname: Borst
mesh_terms: D000818:Animals; D002460:Cell Line; D002843:Chromatin / Q000032:analysis* / Q000648:ultrastructure; D004247:DNA / Q000032:analysis*; D004351:Drug Resistance; D004926:Escherichia coli / Q000032:analysis; D005470:Fluorometry; D008727:Methotrexate / Q000494:pharmacology; D051379:Mice
chemical_list: D002843:Chromatin; D004247:DNA; D008727:Methotrexate