title: Identification of the facultative heterochromatic X chromosome in females of 25 rodent species.
abstract: Treatment of the chromosomes of 25 rodent species with a 50 degrees C hypotonic solution and Giemsa staining permitted identification of the heterochromatic X chromosome in 24 species. With this technique, the facultative of the heterochromatic X chromosome or the facultative portion of large, composite-type X chromosoms is stained darker than the other chromosomes, allowing it to be distinguished from the homologous euchromatic X chromosome in female metaphase cells. Intense staining of the single X chromosome was not observed in male metaphase cells. It is suggested that this differential staining of one of the two X chromosomes might be due to qualitative differences in chromosomal proteins rather than to differences in the degree of chromosomal condensation or in DNA base sequence.
mesh_terms: D000818:Animals; D001399:Azure Stains; D005260:Female; D006570:Heterochromatin / Q000648:ultrastructure*; D007038:Hypotonic Solutions; D008297:Male; D008677:Metaphase; D051379:Mice; D051381:Rats; D012377:Rodentia; D012730:Sex Chromosomes / Q000648:ultrastructure*; D013045:Species Specificity; D013194:Staining and Labeling / Q000379:methods*; D014960:X Chromosome / Q000648:ultrastructure*
chemical_list: D001399:Azure Stains; D006570:Heterochromatin; D007038:Hypotonic Solutions