Miniprep plasmid shows three bands - (Nov/25/2005 )
We always talked about three bands in miniprep or undigested plasmids. but I am no t sure that I understand them right
following is what I think, are they right?
1. in uncompletelt digested plasmid DNA is expected to produce three bands corresponding to the three forms of the plasmid -- supercoiled circular (smallest band), nicked circular (middle band), and linear (largest band). the supercoiled DNA migrate faster than the linear so it always appear smaller than his normal MW size
2. in Miniprep: see 3 bands, one containing CCC DNA (covalently closed circular DNA), one with linear DNA (a small part of your DNA is cut somehow) and one with nicked DNA. They migrate in this order if I'm not mistaken.
See this thread...