title: Nonrandom distribution of sister chromatid exchanges in the chromosomes of three mammalian species.
abstract: The frequency and distribution of mitomycin C (MMC)-induced sister chromatid exchanges (SCEs) were investigated in the fibroblast chromosomes of three mammalian species, Microtus montebelli, Apodemus argenteus and Chimarrogale himalayica, by the fluorescence-plus-Giemsa (FPG) and C-band staining methods, paying special attention to the large C-band area (C-block)-carrying and/or nucleolus organizer region (NOR)-carrying chromosomes. The junctions of heterochromatin and euchromatin (HE-junctions) and NORs were found to be "hot spots" of SCEs in all the species examined: their SCE frequencies were 35.3% and 24.2% in the HE-junction of the X chromosomes of M. montebelli and A. argenteus, and 16.7% and 17.8% in the NORs of the No. 1 chromosomes of M. montebelli and C. himalayica, respectively. In M. montebelli and A. argenteus the SCE frequency was apparently lower in the C-block region than in the euchromatic one, when compared with each other based on equal length, while in C. himalayica no such marked difference in the SCE frequency was found between these two regions of the chromosome. These findings may indicate that occurrence of SCEs is significantly suppressed in the C-block region of M. montebelli and A. argenteus, but not in that of C. himalayica. In addition, the C-blocks of the No. 1 homologue of C. himalayica showed a highly varied individual-to-individual heteromorphism in length. The biological implication of SCEs was discussed in connection with the generation of heteromorphism.
authors.affiliation: Department of Biology, Hirosaki University, Bunkyo-cho, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Satoh
authors.forename: Y
authors.initials: Y
authors.lastname: Obara
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000235:genetics*; D001973:Bromodeoxyuridine; D002871:Chromosome Banding; D002875:Chromosomes; D005260:Female; D007621:Karyotyping; D008297:Male; D008677:Metaphase; D016685:Mitomycin / Q000633:toxicity; D009153:Mutagens / Q000633:toxicity; D012788:Shrews / Q000235:genetics*; D012854:Sister Chromatid Exchange; D013045:Species Specificity
chemical_list: D009153:Mutagens; D016685:Mitomycin; D001973:Bromodeoxyuridine