Gel electrophoresis is normally set up with the negative electrode at the top of the gel and the positive electrode at the bottom of the gel. The DNA products are loaded at the top of the gel, and then a current is applied to separate them. However, when preparing to run a gel, you accidentally switched the locations of the negative and positive electrodes such that the positive electrode is at the top and the negative electrode is at the bottom. You still loaded the DNA products at the top of the gel as normal. What result are you most likely to observe if you apply an electric current to this gel setup?
◦ All DNA molecules will migrate toward the positive electrode.
◦ Shorter DNA molecules will toward the positive electrode, and longer DNA molecules will move toward the negative electrode.
◦ Longer DNA molecules will move toward the positive electrode, and shorter DNA molecules will move toward the negative electrode.
◦ All DNA molecules will migrate toward the negative electrode.
Electrophoresis
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The bacterial cell wall: (a) gram-positive bacterium; (b) gram-negative bacterium.
The cell wall of a Gram-negative bacterium, E. coli
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Samples of the DNA separated by gel electrophoresis