Figure 4.

Model accounting for the preponderance of 5′ site recombinants. (A) The initial junction involves the segment 5′ to the deletion. (B) The initial junction involves the segment 3′ to the deletion. Lengths of homology lying 5′ and 3′ to the deletion being identical, A and B junctions should be equally frequent. Extension of the joint heteroduplex from 5′ to 3′, with respect to the donor strand, is detrimental to incorporation of 3′ SMFs which are beyond the deletion in A and 5′ to the junction in B. Although rare, because of the small distances, junctions occurring within the segment lying between the SMFs and the deletion should invert the SMF preferences. Thin line, recipient strand; thick line, donor strand; Δ, deletion; 3′SMF, side-marking frameshift located 3′ to the deletion; 5′SMF, side-marking frameshift located 5′ to the deletion.