Plasmid DNA migration

Dag Rune Gjellesvik dagrg at
Mon Apr 17 08:53:41 EST 2000

EtBr intercalates the DNA; "sticks" in between the bases. Therefore, the
supercoiling is affected since the primary twist of the helix is stretched,
resulting in less degree of supercoiling. With enough EtBr, you may relax a
supercoiled plasmid, and a closed circular relaxed plasmid may become
supercoiled in the other direction. In addition, EtBr is positively charged.
I didn't know that you may bind so much EtBr to the plasmid that the charge
was reversed, but . . .

Alison Brown wrote ...
>Why does ethidium bromide affect the migration of the different plasmid
>forms in agarose gel electrophoresis?

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