Midiprep from mini prep DNA - (Feb/13/2014 )

Hello,

I am using the Invitrogen midi prep and mini prep kits. I started some cloning and did mini prep to obtain the DNA. I sequenced the DNA and the sequence was correct. So I re-transformed and did midi prep. Is it possible that my midi prep sequence is different from my mini prep DNA? And why would they be different?

No, I don't think it is possible. Only if your transformation has some contamination.and you've picked up some contaminated colony. Otherwise if you transform a clone, you get the clones. Midi and miniprep are different only in scale, right? So your DNA should not change.

It could be different if your repeat transformation came not from a clonaly selected transformed colony but rather from your ligated DNA from your cloning procedure.  If, as neuron indicated above, your growing the same transformation clone for a mini prep followed by growing it for a midi prep then you should be fine.  If you're 're-transforming' (taking DNA from a ligation mixture or some other non-clonaly isolated starting material) then it could be different.