Incorporation of isolated chromosomes and induction of hypoxanthine phosphoribosyltransferase in chinese hamster cells

Evidence is presented for the uptake of radioactive-labeled isolated Chinese hamster chromosomes following incubation with Chinese hamster cells. Metaphases were found which contained radioactive labeled chromosomes in a very low frequency, and in some of the labeled chromosomes only one chromatid was labeled. Incubation of hypoxanthine phosphoribosyltransferase (HPRT)-deficient Chinese hamster cells with chromosomes isolated from HPRT⁺ Chinese hamster or human cells resulted in the appearance of HPRT⁺ cells. Clones derived from these cells were isolated in HA T medium. Cells in mitosis during incubation with the chromosomes yielded three times more HPRT⁺ clones than did cells in interphase. The intraspecies combination involving recipient cells and chromosomes from Chinese hamster origin yielded significantly higher numbers of HPRT⁺ clones than did the interspecies system using human chromosomes and Chinese hamster recipient cells (5×10^–5 and 6×10^–6 respectively). Electrophoresis of HPRT from Chinese hamster cells treated with human chromosomes revealed the pattern of the human enzyme.