FIG. 1.

Schematic diagram of targeted recombination. The synthetic RNA transcribed from the vector pFV1 and the corresponding 3′ end of the Alb4 genome are shown. Viral genes are indicated. There is a 54-nucleotide spacer sequence between the gene 1 fragment and S in pFV1. The sites of the Alb4 deletion, the mutation encoding Q159L, and the relevant restriction sites are shown. The curved line between the genome and the pFV-1 RNA indicates the region in which the crossover must have occurred.