Figure 2

Schematic illustration of mutant fragment generation by overlap extension PCR. During first round PCR (PCR1), the 5' and 3' ends of the target genes, as well as the gentamycin (Gm) resistance cassette are amplified using four gene-specific primers (G-UpF-GWL, G-UpR-Gm, G-DnF-Gm and G-DnR-GWR) and the common Gm-specific primers (Gm-F and Gm-R). This generates three fragments with partial overlaps either to each other (indicated by the blue boxes signifying Gm overlap) or the attB1 and attB2 λ recombination sites (indicated by the green and pink boxes). These purified fragments are then assembled in vitro by overlap extension during second round PCR (PCR2) using common primers GW-attB 1 and GW-attB 2, resulting in a recombination-proficient mutant PCR fragment.