Karyological Characterization of Laboratory Strains of Mongolian Gerbils Using Differential Staining Techniques

Abstract

We analyzed the karyotypes of laboratory strains of Mongolian gerbils showing agouti, black and albino coat colors using conventional and differential staining methods. Of these, three strains have been kept in the author’s laboratory over 30 years and one strain was obtained from a supplier. The conventionally stained karyotypes of the gerbils were fundamentally identical to those in previous studies, consisting of 2n=44 (FNa=74) with 42 autosomes: 16 pairs of bi-armed (metacentrics, submetacentrics, and subtelocentrics) and 5 pairs of uni-armed chromosomes (acrocentrics), a large-sized metacentric X chromosome and a small-sized submetacentric Y chromosome. In addition, the G- and C-banded karyotypes were identical to those in previous studies. Notably, our strains carry no intraspecifical karyological variation and their karyotypes are quite stable without a polymorphic state, except for heteromorphic variations caused by size differences as a usual phenomenon. Moreover, the unique C-bands were found in Nos. 5 and 13 chromosomes but fluorescent staining results (using quinacrine mustard and chromomycin A₃) at the unique C-band regions differed between Nos. 5 and 13 chromosomes. This fact indicates that such a difference has been caused by higher molecular structures containing proteins rather than nucleotide contents.