C. botulinum cells are typed by which toxin genes a strain possesses, not on the basis of surface antigens. Isolates can be typed in a single PCR reaction that includes primer pairs specific for each of the four major toxin genes: types A, B, E, and F. Because multiple products are sought in a single reaction, this is called multiplex PCR. Each lane in the agarose gel was loaded with multiplex products from different isolates of C. botulinum and subjected to electrophoresis. Consider the agarose gel electrophoresis results. Known samples were loaded in lanes 2–5: Lane 1, DNA size markers; lane 2, type A (cntA); lane 3, type B (cntB); lane 4, type E (cntE); lane 5, type F (cntF). Unknown strains were used for lanes 6, 7, and 8.
Lindström, M., et al. 2001. Appl and Environ Microbio 67:5694
1st attempt
Part 1 (0.3 point)
Feedback
Which toxin gene amplicon represents the largest DNA fragment?
Choose one:cntFcntBcntAcntE
Part 2 (0.3 point)
Feedback
Of the three unknown C. botulinum sample lanes, which lane contains an unknown strain of C. botulinum that possesses only two of the major toxin genes?
Choose one:lane 6lane 7lane 8All of these lanes do.None of these lanes do.
Part 3 (0.3 point)
Feedback
What could be done to cause the organism that was represented in lane 6 to encode all four major toxin genes?
Choose one:A. mix the template genomes of both lane 6 and lane 7B. genetic engineering where an additional gene is added to the genomeC. removal of half of the primers from the multiplex PCR experimentD. addition of more primers to the multiplex PCR experiment