Figure 6.

Recombination between attL and attR via the unfavoured synapse is not prevented. (A) Expected recombination products from pPARX18L^AA encoding attL^AA and attR in head to tail orientation. The att sites are represented as described in the legend to Figure 5A except that the central dinucleotide in the attL site has been changed to 5′AA. Synapsis of attL^AA and attR in the complementary format will be permitted but formation of products is prevented (‘X’) by the mismatch at the cleavage sites. Synapsis with the attL^AA and attR sites in the non-complementary arrangement will give rise to products where the DNA between the att sites is inverted. Recombination by attL x attR^AA in pPARX18R^AA is also expected to give an inverted product with the same restriction fragments as pPARX18L^AA; Xh, XhoI. The fragment sizes for the substrate and the expected inversion products are indicated. (B) Inversion of pPARX18L^AA and pPARX18R^AA by Int E449K. Recombination reactions were performed under standard conditions and then digested with XhoI. The substrates and products are indicated. M, molecular weight markers.