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DNA purity by Agarose Gel Electrophoresis - (Jul/29/2006 )

Hi, I'm doing a datasheet on the experiment as named above..

But I dont know how to comment on my DNA purity based on the results. I have a lambda/Hind III marker with molecular sizes of 23130, 9416, 6557, 4361, 2322, 2027, 564 and 125.

The molecular size of my plasmid pBR322 is 4361bp.

How do I analyze the purity of the plasmid?? I've tried searching the net about DNA purity via AGE, but cant find any results. Could you help??


I assume you are working with purified plasmid of ~4.3 kb. You will see several bands. These are isomers of the same plasmid with different configuration. The predominant one should be supercoiled form. you will have open circle, and possibly linear forms. Sometimes dimer also exists. So dont be surprised if you see multiple bands of plasmid..These will be exact 4.3 kb as you expected, as they are mostly in circular forms, not linear DNA as your markers. If there is RNA contamination, they usually migrate much fast in a rather diffused band. If there is chromosomal DNA contamination, they show up ~20 kb position.

Read "Molecular Cloning" for more info. Most labs have this "bible".