Figure 2 : Schematic representation of DNA recombinations to recover end-deleted BACs.

Step 1: Shows the Cre recombination of circularized phage P1 DNA (P-G-E) with the end-deleted BAC DNA (B-A-C) to generate a co-integrate. The phage packaging
site “pac site” and the Cre gene are indicated in the phage DNA by the thick solid bar and the X, respectively.
Step 2: Shows the BAC DNA packaged in the phage P1 head, its recombination after entry into cells by newly synthesized Cre protein, and circularization into a BAC
plasmid. If the length of DNA (B-A-C) exceeds the headful packaging capacity of ~110 kb, then the second loxP site (indicated by the thick arrows) would not fit in
the phage head and the DNA cannot circularize by loxPCre recombination after entry into cells [46]. It leads to the BAC DNA not being rescued. Note that the Cre
gene is also lost upon circularization of the truncated BAC DNA.

Chatterjee et al.Molecular Biology and Genetic Engineering  2014 2:2DOI : 10.7243/2053-5767-2-2