Figure 7-4: Insertion and looping out of specialized transducing phage. The λ gal+ can insert into the chromosome either by site-specific recombination at att or by homology-dependent recombination in host DNA between gal and attλ. The product (a heterogenote) has two copies of gal, separated by λ DNA. During growth of the strain, the λ gal can occasionally loop out through homology-dependent recombination. Depending on the position of the crossover point, the haploid derivative can carry either the gal gene of the original chromosome or that brought in by the phage. Looping out to give the chromosomal gene happens at about 10-3 per generation. The rate for the phage-derived gene (in the case, gal+) is lower and depends on the extent of homology to the left of gal. The reciprocal product (an excised λ gal, which, if formed, does not replicate and is therefore diluted out by growth) is not shown. (for better image quality, click here for tif image, which may be quite large; may also require screen refreshing plus special software to view; or view larger tif in separate window)

Figure 7-1, Figure 7-2, Figure 7-3, Figure 7-4, Figure 7-5, Figure 7-6, Figure 7-7, Figure 7-8

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