Nonrandom arrangement of metaphase chromosomes in cultured cells of the Indian deer, Muntiacus muntjak.

Abstract

The Indian deer, <i>Muntiacus muntjak, </i>with its low number of individually identifiable chromosomes (♂, 2n = 7), is a suitable material for studies on the spatial interrelationships among metaphase chromosomes on the equatorial plate. Cultured monolayers not subjected to colchicine or hypotonic treatments were analyzed in situ. The emphasis mainly was placed on determining the locations of the centromeres of the six large chromosomes, which usually occupied peripheral positions at the equator. The frequencies found of certain patterns of chromosome arrangement deviated significantly from what would be expected if these patterns were random. Cells in which homologs were next to each other were more frequent than expected. In configurations in which no homologous chromosomes occupied adjacent positions, symmetrical radial arrangements, based on homology or proximity in size, were favored. The position of the Y chromosome usually was close to the centromeric region of the X-autosome, which might be a consequence of a heterochromatic association or partial homology between the X and Y. Factors relevant to the chromosome arrangement on the equatorial plate may be somatic pairing, symmetrical spatial interrelationships between chromosomes based on homology or size, and heterochromatic association.