Variation of stemline karyotype in a HeLa cell line.

100 karyotypes of a HeLa cell line (modal number 69) were studied in details. It was observed that the stemline cells of this "triploid" somatic cell population showed high degree of chromosomal polymorphism. It has been discussed that the stemline cells have number of extra chromosomes (or parts of chromosomes) which are not essential for the genetic integrity of this cell population. A loss of some of these chromosomes (or their parts) does not induce any appreciable change in the genetic make-up of these cells. The broken chromosomes lose their identity and are grouped together with the non-homologues, when the Denver system of classification is followed. However, it has been argued that in absence of any other acceptable system for classification, the Denver system can still be employed for analyzing human chromosomes both at diploid and abnormal heteroploid level. It has been held in contrast to the pseudo-stemline concept that these cells in general, have the essential genes in common and are responsible for the genetic make-up of this cell line and constitute together the stemline of this somatic cell population.