Fig 7.

Selected recombination zones and the probability of generating a recombinant with exactly the same sequence as XMRV. A 415-nt region in the 5′ UTR and a 982-nt region in RT are defined as the selected recombination zones. A crossover within each of these selected recombination zones was observed in all RCRs and is postulated to be essential for formation of an RCR. Using the data from the recombinants from infections A to F, the number of recombinants that used the same region for any of the 6 crossover switches between PreXMRV-1 and PreXMRV-2 that generated XMRV is listed (red boxes). For example, in the 5′ UTR, 15 of the 26 clones analyzed used the same region as XMRV for a crossover. Multiplying together the number of clones that used the same homology region as XMRV for crossover events (12/26 × 1/26 × <1/34 × <1/34 × <1/34 × <1/34), the probability of generating XMRV is <1.3 × 10⁻⁸. Dark gray shading, PreXMRV-1 sequences; light gray shading, PreXMRV-2 sequences.