recA-dependent and recA-independent N-ethyl-N-nitrosourea mutagenesis at a plasmid-encoded herpes simplex virus thymidine kinase gene in Escherichia coli.

recA-dependent and recA-independent N-ethyl-N-nitrosourea mutagenesis at a plasmid-encoded herpes simplex virus thymidine kinase gene in Escherichia coli.