[Karyotype characteristics of continuous cell lines. II. The variability and balance of the chromosome set of M-HeLa cells].

A cytogenetic study of three M-HeLa sublines of common origin but differing in cultivation technique was undertaken with G-, C- and Ag-staining. The sublines differ in their normal and marker chromosome contents. The marker chromosomes were completely identified in all the sublines. This enabled us to employ a new cytogenetic method of karyotype reconstruction. The reconstruction of normal chromosomes from fragments entering into the marker composition allowed to determine the total content of normal chromosomes in each cell. This total content does not vary somewhat substantially within one subline in spite of the intercellular karyotype heterogeneity, and this proves the balance of genomes within a given subline. The reconstructed karyotypes of separate cells made it possible to build a generalized reconstructed karyotype of each subline. In this karyotype obligatory and minimal should be the human diploid chromosome set. Moreover, in each subline the 1st and 5th chromosomes are extracopied. In addition to this stable component, occurring in all the cells, in some cells chromosomes 7 9, 12, 14, 16 and 17 may also be extracopied. The marker formation involved mainly centromeric regions of the 1st, 3rd and 5th chromosomes. With the existing chromosome variability the selection plays the main role in the formation of cell populations cultivated in different ways.