Amplification and loss of dihydrofolate reductase genes in a Chinese hamster ovary cell line.

摘要: Abstract During stepwise increases in the methotrexate concentration culture medium, we selected Chinese hamster ovary cells that contained elevated dihydrofolate reductase levels which were proportional to number of gene copies (i.e., amplification). We studied individual underwent initial steps resistance by using fluorescence-activated cell sorter technique. Such constituted a heterogeneous population with differing levels, and they characteristically lost enzyme when grown absence methotrexate. The progeny high behaved differently could lose all or variable numbers amplified genes.