A methodology has been developed to enable long-term cultivation of euploid (normal) cells from human and animal sources without the development of aneuploidy. This method uses pretested fetal calf serum and careful control of pH and temperature. It allows for the reliable establishment of stable cell cultures from minute skin biopsies taken from any individual. Clones of mammalian cells with chromosomal markers have been isolated from x-irradiated and non-irradiated cell cultures. The technique has been applied to chromosome delineation in large numbers of human subjects, determination of chromosomal sex in patients, and the study of spontaneous and induced genetic changes in somatic mammalian cells. It has also been used to compare metabolic differences between normal and cancerous cells. The method also enables the long-term cultivation of normal cells without the chromosomal instability often seen in animal cell cultures. The cells maintain their karyotype integrity and can be grown for extended periods. The technique has been successfully applied to various animal tissues, including those of the Chinese hamster and the American opossum. The method allows for the isolation of clonal populations and the study of genetic markers. It has also been used to investigate the effects of radiation on cell growth and to determine the minimum dose required to produce chromosome breaks in euploid human cells. The technique has potential applications in medical diagnostics and therapeutic procedures, as it allows for the cultivation of cells from individual patients. The method involves careful handling of cells to minimize trauma and ensure optimal growth conditions. The results demonstrate the feasibility of long-term cultivation of euploid cells and the importance of maintaining optimal environmental conditions to prevent chromosomal abnormalities. The study highlights the potential of this technique for genetic research and the development of cell banks for therapeutic use.A methodology has been developed to enable long-term cultivation of euploid (normal) cells from human and animal sources without the development of aneuploidy. This method uses pretested fetal calf serum and careful control of pH and temperature. It allows for the reliable establishment of stable cell cultures from minute skin biopsies taken from any individual. Clones of mammalian cells with chromosomal markers have been isolated from x-irradiated and non-irradiated cell cultures. The technique has been applied to chromosome delineation in large numbers of human subjects, determination of chromosomal sex in patients, and the study of spontaneous and induced genetic changes in somatic mammalian cells. It has also been used to compare metabolic differences between normal and cancerous cells. The method also enables the long-term cultivation of normal cells without the chromosomal instability often seen in animal cell cultures. The cells maintain their karyotype integrity and can be grown for extended periods. The technique has been successfully applied to various animal tissues, including those of the Chinese hamster and the American opossum. The method allows for the isolation of clonal populations and the study of genetic markers. It has also been used to investigate the effects of radiation on cell growth and to determine the minimum dose required to produce chromosome breaks in euploid human cells. The technique has potential applications in medical diagnostics and therapeutic procedures, as it allows for the cultivation of cells from individual patients. The method involves careful handling of cells to minimize trauma and ensure optimal growth conditions. The results demonstrate the feasibility of long-term cultivation of euploid cells and the importance of maintaining optimal environmental conditions to prevent chromosomal abnormalities. The study highlights the potential of this technique for genetic research and the development of cell banks for therapeutic use.