| abstract |
There is described a method for obtaining a eukaryotic cell containing in its DNA multiple copies of a GS gene, comprising: transforming a eukaryotic glutamine auxotroph with a GS gene; selecting transformant cells containing the GS gene; and culturing the selected transformant cells in a medium which lacks glutamine or in which the amount of glutamine is progressively depleted, the GS gene being of a character such that, or the conditions employed during the culturing step being such that, the GS gene is so weakly transcribed that the cells in which the GS gene has been amplified are selected. |