A research group has just received four strains from a one of their collaborators. Following their usual practice, a student is using
colony PCR to confirm the identities of the four strains A-D before starting work. The lab has diagnostic primers for all four strains. The expected sizes of the PCR products for strains A-D are 680 bp, 1100 bp, 572 bp and 462 bp, respectively. Unfortunately, the student who runs the gel forgets to write down which sample has been run in each lane. Analyze the gel on the right. No PCR product can be detected in lane 5. The position of the 3 kb marker is indicated. Place size labels for a few of the other markers. Which strain’s PCR product has been loaded into:
Lane 2 Lane 3 Lane 4 Lane 5
Explain your reasoning. What might the lack of a product in Lane 5 indicate?