To determine the nature of the recombinant RNA 3s derived from the 163-nt repeat-deletion mutants, we again purified the recombinant RNA 3s of C1C2 T2B T3 Á163(A) , C1C2 W2B T3 Á163(A) , C1C2 T2B T3 Á163(G) and C1C2 W2B T3 Á163(G) , used RT-PCR to amplify the recombinant sequences, cloned the RT-PCR products and sequenced them. The sequences of the recombinant RNA 3 derived from C1C2 T2B T3 Á163(A) contained the 5 0 -proximal 2082 nt from TAV RNA 3 and the 3 0 proximal 310-nt 3 0 NTR of CMV RNA 1 ( Figure 5A ). The CMV RNA 1 NTR sequence was identical to that present in the recombinant RNA 3 derived from C1C2 T2B T3. However, the TAV RNA 3 sequence was 22 nt longer than that of the recombinant RNA 3 derived from C1C2 T2B T3 (compare Figures 3A  and 5A) , suggesting that the first 163-nt repeat might have a role in determining the crossover site on one of the participating RNAs, despite not affecting the crossover site on the other participating RNA. By contrast, the sequence of the recombinant RNA 3 derived from C1C2 T2B T3 Á163(G) was exactly the same as that derived from C1C2 T2B T3 (compare Figures 3A and 5B) , indicating that the second 163-nt repeat had no role in determining the crossover sites on either RNA.