SUMMARY

Two independently derived cell lines which carry the herpes simplex type 2 thymidine kinase gene have been examined for the presence of HSV-z-specific DNA sequences. Both cell lines contained I to 3 copies per cell of a sequence lying within map co-ordinates o'2 to o'4 of the HSV-2 genome. Revertant cells, which contained no detectable thymidine kinase, did not contain this DNA sequence. The failure of EcoRI-restricted HSV-2 DNA to act as a donor of the thymidine kinase gene in transformation experiments suggests that the gene lies close to the EcoRi restriction site within this sequence at a map position of approx. o'3. The HSV-2 kinase gene is therefore approximately co-linear with the HSV-I gene