title: Topological state of DNA in polytene chromosomes.
abstract: A new microfluorometric method was developed for measuring two topological characteristics of DNA in isolated nuclei, chromosomes and other DNA containing structures: (1) the relative amount of the topologically non-closed DNA (tncDNA) and (2) the supercoiling density of the topologically closed unconstrained DNA (tcDNA). The method was applied to isolated polytene nuclei and chromosomes of Chironomus thummi. The relative amount of tncDNA was found to be 0.21. Evidence in favour of the tncDNA localization in transcriptionally active loci (puffs) of the polytene chromosomes is presented. The supercoiling density of tcDNA localized, presumably, in inactive loci (bands) of the polytene chromosomes is about -0.001.
authors.affiliation: Institute of Cytology and Genetics, Siberian Branch of the USSR Academy of Sciences, Novosibirsk.
authors.forename: A D
authors.initials: AD
authors.lastname: Gruzdev
authors.forename: M A
authors.initials: MA
authors.lastname: Shurdov
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000737:chemistry* / Q000648:ultrastructure; D002683:Chironomidae / Q000737:chemistry; D002843:Chromatin / Q000648:ultrastructure*; D002875:Chromosomes; D004247:DNA / Q000302:isolation & purification* / Q000648:ultrastructure; D004278:DNA, Superhelical / Q000648:ultrastructure; D003851:Deoxyribonucleases; D004996:Ethidium; D009690:Nucleic Acid Conformation; D012260:Ribonucleases; D012469:Salivary Glands / Q000737:chemistry; D014158:Transcription, Genetic
chemical_list: D002843:Chromatin; D004278:DNA, Superhelical; D004247:DNA; D003851:Deoxyribonucleases; D012260:Ribonucleases; D004996:Ethidium