Figure 2.

Recombination events facilitated by introduction of kan cassette structurally organized as a hairpin loop. The φ6K1 recombinant virus contains the M-segment with a kan cassette. Isolation of clear plaques from unstable transducing virus confirmed the recombination between M and S or L segments (A,C). This stable isolated virus φ1697 (A,B) did not have the kan cassette in the M-segment. The 3′ end of M-segment of φ6K1 (3754–5303 bp) was recombined heterologically with the 3′ end of the S segment (2858–2948 bp). Only 6 bp of similarity existed between two segments. The φ 1703 (C,D) virus did not have a kan cassette, as did φ1697, and lacked the P13 gene. The φ1703 is a recombination product between the 3′ end of the M-segment of φ6K1 and L-segment of wildtype φ6. There were only two identical base pairs observed. Recombination was also observed in an S segment of CS that was derived from φ6K1 (E,F). The S segment demonstrated an internal deletion of 189 nucleotides within the 3′ noncoding region. The segment was incorporated into φ1712. The clear plaque variant φ1713 produced by the carrier culture was a recombinant between the segment M from native φ6 and the 3′ end of segment S from φ1712 that contained the internal deletion described above. Only six identical base pairs were observed. Based on Mindich et al. (1992).