Biology Forum › Cell Biology › DNA plasmid lab
October 16, 2009 at 9:07 pm #12033
I’m new here so I’m hoping I’m doing this correctly! I am a sophmore at a small private university and am studying cell biology. We just completed a lab on plasmid DNA and ran an agarose gel producing two bands. My professor wants to know why there are two bands of undigested PBR322 (I assume the plasmid?) when the DNA is circular.
I know a few things already:
The smaller the particle the faster it moves through the gel.
Supercoiled DNA moves the fastest so chances are its the lower bar.
We did not cut the DNA so we can not assume size difference.
Could anyone help me figure out what the other piece of DNA could be?
Thanks so much.
October 16, 2009 at 10:53 pm #93809
If the smaller band is supercoiled DNA, than the other one will probably be not-supercoiled,don’t you think?
October 16, 2009 at 11:23 pm #93812mithParticipant
flaunting the private university are we?
October 17, 2009 at 12:24 am #93818
Right, I figured that much, but what type of DNA is it? Linear? CIrcular? Has it been nicked? Or do I have any way of knowing?
And I meant nothing with the private univeristy specification. I was pointing out my resources and our labs are terribly limited.
October 17, 2009 at 12:45 am #93819
It’s all circle, just the level of supercoiling differs 😉
October 17, 2009 at 1:31 am #93820MrMisteryParticipant
DNA exists as a mix of topoisomers
October 17, 2009 at 3:29 am #93824quote MrMistery:DNA exists as a mix of topoisomers
OK, now you should explain, what are topoisomers 😆
October 17, 2009 at 4:32 am #93827
Well, a topoisomers are varying forms of closed circular dna molecules. So, are you saying (or should i say pointing me to the fact) that the other band of DNA is a topoisomers? Sorry if I sound slow at this…its kind of a first time for me having to explain what I’m doing in lab.
October 17, 2009 at 5:06 am #93828
As you wrote, the supercoiled DNA will move faster than the relaxed one 😉
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