title: Satellite DNA in large marker chromosomes of methotrexate-resistant mouse cells.
abstract: The additional segments of five large marker chromosomes of methotrexate-resistant mouse melanoma PG19T3 cells are shown to consist of C-banding material. In situ hybridization indicates that these additional segments also contain a high proportion of sequences that will cross hybridize with mouse satellite DNA. Analytical density gradient centrifugation suggests that up to 60% of the DNA in the additional segments may be in the form of satellite DNA. Incorporation of bromodeoxyuridine for one complete S phase and staining with the Hoechst 33258 fluorescence plus Giemsa technique reveals complex asymmetries within the additional segments. These asymmetries are interpreted as showing a large repeating unit, which is likely to be involved in the amplification of the dihydrofolate reductase gene.
mesh_terms: D000818:Animals; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D002871:Chromosome Banding; D002875:Chromosomes / Q000032:analysis*; D004276:DNA, Satellite / Q000032:analysis*; D004351:Drug Resistance; D006570:Heterochromatin / Q000032:analysis; D008545:Melanoma; D008727:Methotrexate / Q000494:pharmacology*; D051379:Mice; D009693:Nucleic Acid Hybridization; D012854:Sister Chromatid Exchange
chemical_list: D004276:DNA, Satellite; D006570:Heterochromatin; D008727:Methotrexate