DNA plasmid lab

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relamberth
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DNA plasmid lab

Post by relamberth » Fri Oct 16, 2009 9:07 pm

Hi everyone:
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.

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JackBean
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Post by JackBean » Fri Oct 16, 2009 10:53 pm

If the smaller band is supercoiled DNA, than the other one will probably be not-supercoiled,don't you think?
http://www.biolib.cz/en/main/

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mith
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Post by mith » Fri Oct 16, 2009 11:23 pm

flaunting the private university are we?
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relamberth
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Post by relamberth » Sat Oct 17, 2009 12:24 am

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.

Thanks.

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JackBean
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Post by JackBean » Sat Oct 17, 2009 12:45 am

It's all circle, just the level of supercoiling differs ;)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

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MrMistery
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Post by MrMistery » Sat Oct 17, 2009 1:31 am

DNA exists as a mix of topoisomers
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JackBean
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Re:

Post by JackBean » Sat Oct 17, 2009 3:29 am

MrMistery wrote:DNA exists as a mix of topoisomers

OK, now you should explain, what are topoisomers :lol:
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

relamberth
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Re: DNA plasmid lab

Post by relamberth » Sat Oct 17, 2009 4:32 am

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.

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JackBean
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Post by JackBean » Sat Oct 17, 2009 5:06 am

exactly ;)

As you wrote, the supercoiled DNA will move faster than the relaxed one ;)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

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