title: Mastomys (=Praomys) natalensis is not a Rattus (Mammalia: Rodentia): karyological evidence.
abstract: Certain past studies have suggested that the taxa Mastomys (= Praomys) and Rattus were closely allied phyletically. We here present detailed (C- and G-banding and NOR's) comparisons of the karyotypes of M. natalensis (2n = 36) and R. norvegicus (2n = 42). A standardized G-banded karyotype of M. natalensis is also presented. About 45% of the G-banded karyotype of M. natalensis is homologous with that of R, norvegicus. Autosomal constitutive heterochromatin is nearly equivalent in the two species; the X and Y chromosomes of M. natalensis, however, have exceptionally large heterochromatic segments. Both species possess three pairs of NOR's, but adjacent G-banded regions are homologous for only one of these. Primarily on the basis of overall G-band homology, we regard the two taxa as only distantly related.
mesh_terms: D000818:Animals; D002871:Chromosome Banding; D002875:Chromosomes / Q000648:ultrastructure; D005260:Female; D006570:Heterochromatin; D007621:Karyotyping; D008297:Male; D009697:Nucleolus Organizer Region; D010802:Phylogeny; D051381:Rats; D012377:Rodentia / Q000145:classification* / Q000235:genetics
chemical_list: D006570:Heterochromatin