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. 2010 Jul 26;107(32):14116–14121. doi: 10.1073/pnas.1007795107

Fig. 1.

Fig. 1.

Strategy for examining TLS opposite a Tg lesion carried on the leading or lagging strand DNA template of a duplex plasmid. (A) Structures of 5R,6S and 5S,6R Tg. (B) The target 16-mer sequence containing a Tg, and the sequences of the N-terminal portion of the lacz′ gene in the lagging strand (pSB) and the leading strand (pBS) vector with a Tg lesion are shown. (C) Strategy for TLS assays. (Left) The locations of the Tg, the lacZ′ gene, SV40 origin, and the kan gene are shown on the vector. (Right) In the duplex plasmid, the DNA strand containing the Tg also carries the wild type kanamycin gene (Kan+) so that TLS through the Tg will produce a blue colony on LB/Kan plates with IPTG and X-gal. The other DNA strand harbors an SpeI sequence opposite the Tg and carries the kan- gene. Because the SpeI sequence puts the lacZ′ sequence out of frame, replication of the Tg-containing strand by template switching would generate white colonies.