| 摘要 |
PURPOSE:To plasmid vector having tetracycline-resistant (TC-resistant), amplicillin-resistant (Ap-resistant) and trimethoprim-resistant (Tp-resistant) markers, containing scission sites of various kinds of restricted enzymes, and capable of loading extrinsic DNA fraction. CONSTITUTION:A plasmid vector having Tc-resistant gene, Ap-resistant gene and Tp-resistant gene as markers. The plasmid can be prepared as follows: A plasmid vector pBR 322 having Tc-resistant and Ap-resistant markers is treated with a restricted enzume EcoRI to break the sites other than the insertion inactivated site, and then treated with enzyme nuclease SI to obtain straight-chain DNA having smooth end. Separately, the DNA fraction containing dihydrofolate reductase gene obtained from Escherichia coli K12 strain is shortened, and connected and cyclized with the above straight-chain DNA to obtain mixed plasmid. The plasmid is introduced into Escherichia coli K12 strain and the strain is cultured to obtain plasmid vector pTP30-5 having Tc-resistant, Ap-resistant and Tp-resistant markers and containing 6.3 kilo base pairs. |
