Circular ligation product migration on gel? - (Jul/30/2007 )

Hi, I have quite a trivial question for some of you:
I am trying to ligate a 0.8kb insert into a 7kb plasmid. If the ligation is succesfull, the insert is in, how the new 7.8kb construct will it look on a gel - since it is circular, will it run faster then the linearized 7kb plasmid? Or will it run slower, since it is bigger then the linearized plasmid? Thank you.

open circular plasmids will run slower then their linear equivalents. So what you will see is are a few high molecular weight bands, which appear to exceeding 7.8kb in size. Note ligation is a bit messy process, so while only circular plasmids will replicate in a cell, the ligation mix will contain linear vector and insert ligations, insert+insert ligation, insert+insert+vector linears... and so forth.