FIG. 2.

(A) Specificities of primers for selective PCR after RT with random primers. In cDNAs from cells infected singly with PV M1 or S2 and in PV M1- and S2-double-infected cells, the M or S primers specifically recognize the cDNA of PV M1 (a band of 638 bp; lanes 1 and 8) or PV S2 (a band of 473 bp; lanes 6 and 9), respectively. With the S up and M down primer combination, cDNA prepared from double-infected cells allows amplification of recombinant cDNA (a band of 471 bp; lane 10). In lane 11, this band was reamplified with the same primer combination. If PV M1 and PV S2 RNAs from separately infected cells are mixed prior to RT-PCR, parental but not recombinant bands of 471 bp are found (lanes 13 to 15); lane 16 is a reamplification of the DNA shown in lane 15. The band marked with an asterisk is due to spurious priming of M down primer on PV S2 cDNA (see the text). Lanes 4 and 12 are 100-bp DNA ladders. +, present. (B) Sequence obtained from cDNA of the recombinant (Recomb.; panel A, lane 11) aligned with the sequences of PV S2 and PV M1, starting at nt 2688. The recombination locus is boxed and comprises nt 2899 to 2914 (numbering according to PV S2).