FIG. 4.

PCR analysis of fMHV recombinants. In each experiment, RT-PCR was used to amplify regions of RNA isolated from cells infected with each of four independent isolates of fMHV or two MHV controls. The controls, Alb129 (13) and Alb203 (7), are MHV mutants that were also obtained by targeted recombination between Alb4 and pFV1-related donor RNAs; both are phenotypically wild type and are isogenic with wild-type MHV in the region under analysis. PCR products were analyzed by electrophoresis in 0.8% agarose gels stained with ethidium bromide. Sizes of relevant standard (std) marker DNA fragments are indicated on the right or left of each gel. PCR primers (Table 1) used in each experiment, their loci in the MHV or fMHV genomes, and the predicted sizes of the PCR products or restriction fragments of the PCR products are indicated on the right.