Heterogeneity and balance of chromosomes in human cell line M-HeLa-76: analysis of 100 karyotypes.

The cell subline M-HeLa-76 with the modal chromosome number 49 was used to define the level of karyotypic variability. By means of a G-banding technique, 100 metaphase plates were analyzed. Among them, 11 different karyotypes were found to range from 2% to 34%. Most probable evolutionary pathways of cell karyotypes within the cell subline were demonstrated. Determination of the origin of all marker chromosomes (32 in all) and unique structural rearrangements (16) revealed a nonrandom distribution of chromosome breaks. These are primarily centromeric regions of chromosomes 3 and 5. Identification of the overall chromosome material in the cells of each karyotype via karyotype reconstruction showed their close similarity in spite of differences in the sets of normal and marker chromosomes. On the basis of reconstructed karyotypes (RK) of each cell group, a generalized reconstructed karyotype (GRK) of the cell line was obtained. This permitted the conclusion of a balanced chromosome set in a cell population as a whole and obligatory retention of diploidy in all chromosomes of a normal set. The role of variability and selection in the evolution of cell populations in vitro is discussed.