DNA content measurements and an improved idiogram for the Indian muntjac

The Indian muntjac, an asiatic deer, has the lowest diploid chromosome number among mammals (female 2N = 6; male 2N = 7). Using flow cytometric quantification of propidium iodide-stained cells, we determined the DNA content of muntjac cells to be 94% that of human. This suggests that the muntjac may serve as a model for investigation of karyotypic evolution and rearrangement. In order to facilitate future comparative gene mapping studies, computer-aided analysis of digitized metaphase chromosomes allowed development of a detailed Indian muntjac G-banded idiogram incorporating both ISCN-type nomenclature and quantitative estimates of the size of each band and position.

Constitutive heterochromatin of Indian muntjac chromosomes revealed by DNAse treatment and a C-banding technique

A karyotype of a female Indian muntjac, Muntiacus muntjak vaginalis, was described. The karyotype was unique in that No. 1 and No. 3 homologous pairs were heteromorphic with respect to the size of their secondary constrictions. In these pairs, one of the homologs always had a longer secondary constriction than that on the corresponding homolog. Heterochromatin in the secondary constriction region was visualized with difficulty by a C-banding technique, but was demonstrated clearly by a DNase treatment followed by Giemsa staining, which also revealed the size difference of the secondary constriction. Centromeric constitutive heterochromatin of No. 1 chromosome was also found to differ in size between the homologs. On the basis of the heteromorphic character of No. 3 chromosome, or an X-autosome complex, it was possible to confirm autoradiographically that X-inactivation had occurred at random.