Uppgift
Explain how gel electrophoresis can be used to analyze different conformations of plasmid DNA. Discuss how the migration patterns of these conformations differ and how comparing them with the ladder (marker) helps interpreting the gel results and understand the structure of the plasmid DNA. (4p) Max 150 words. Answer in English.
Answer
The electrophoresis has two differently charged ends, one positive and one negative. The plasmids get injected into the gel electrophoresis in a well from the negatively charged end. When we then give it a current, the plasmids will travel to the positive end (because DNA is negative). The bigger the plasmid is, the further it will travel, because it has more negative charges than a small one. Supercoiled and circular DNA will meet different amount of friction, since they have different forms, which will result in one traveling further than the other even though they have the same size.
The marker will help identify how many base pairs the plasmid have. But if we analyze two of the same plasmids and they travel different distances, then it means that they have different conformations where one is supercoiled and the other is circular. The circular meets more friction.
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