Isolation of the chicken thymidine kinase gene by plasmid rescue

The bacterial plasmid pBR322 was used as a vehicle to isolate genes coding for selectable markers from higher eukaryotes. The chicken thymidine kinase (tk) gene was obtained as a 2.2-kilobase EcoRI/HindIII insert in pBR322. The cloned gene transforms tk- animal cells with an efficiency equal to that of the cloned herpes simplex virus-1 tk gene