[Origin of marker chromosomes in a continuous human cell line]

The karyotypes of L-41 cells (subline J-96) and those of cell strains obtained from RH strain in the course of multiple passages and mycoplasm infection were studied using the GTG technique. All the RH strains contained chromosomes with bands similar to Hela and other cell strains well-adapted to permanent growth in the tissue culture. The origin of marker chromosomes was studied. The activity of G-6-PDG was detected cytochemically in cells having an X-chromosome. A decrease in alkaline phosphotase activity corresponded to the reduction of the number of G-chromosomes. Possible causes of the arising of marker chromosomes are discussed.