Chromosome distribution in a23 Chinese hamster fibroblasts.

This study deals with a systematic chromosome position analysis of 116 anti-mitotic and hypotonic treated a23 chinese hamster cells. No chromosome or pair of chromosomes was found to be located nearer the center or the periphery of the metaphase plate than would be expected by the reference distribution. The homologous chromosomes of pair 2 lie nearer to each other but they do not form a specific angle. The same relative position was shown for the chromosome groups 1-2, 1-E1 and 2-E5 (E standing for an extra chromosome). On the other hand the chromosomes of the combinations X-7, X-8, 7-8, 8-11 and X-E2 were lying further from each other, while chromosomes 10-E1 had a greater mean angle. The non random distribution of the chromosomes 1 and 2 may be interpreted as function of their possibly more frequent participation in the organization of nucleoli. -- To obtain more information about the influence of preparation techniques on the alteration of the chromosome position in metaphase plates, this study deals with some overall considerations about chromosome position. It is shown that in a23 cells the smaller chromosomes do not tend to lie nearer the metaphase plate center (as it happens in human cells). Also a significant correlation between the chromosome position with respect to the metaphase plate center and the mean interchromosomal distances was not found in this type of cells.