[Transformation of mice by a prokaryotic gene for dihydrofolate reductase]

In mice obtained after microinjection into the male pronucleus of fertilized eggs of the plasmid, containing the bacterial gene of dihydrofolate reductase (DHFR), under the control of the early promotor of the simian virus 40 (SV40), an integration of the foreign DNA into the mouse genome is found. About 30% of the treated animals contain the integrated plasmid DNA sequences, i.e. are transgenic. In 2 of 7 mice, containing the introduced plasmid in their genome, the methotrexate-resistant DHFR activity is found in the kidney and spleen, which may be due to the expression of gene DHFR. The plasmid DNA sequences and the ability to synthesise the methotrexate-resistant enzyme DHFR are transmitted to the next generation of mice.