Figure 6.

Replisome invasion/template switch model of λ recombination. The diagram depicts a recombination event between the tip of a rolling circle (circle not shown), and another replicon (either one of the replisomes of a theta-mode intermediate, or the replisome of a second rolling circle). (Top) A Red-processed dsDNA end (Beta bound to a ssDNA overhang generated by Exo) invades a replication fork and promotes annealing to the lagging strand template. (Middle) Beta captures the leading strand and promotes a template switch, such that the leading strand polymerase now uses the incoming strand as a template. (Bottom) Template switch (TS) model invokes a redirection of the replisome to the incoming strand. The template switch then connects one arm of the original replisome to the invading duplex (i.e., the recombination event). As before, red trapezoid, λ Exo; blue circles, λ Beta. Yellow oval represents the replisome.