DNA Supercoiling

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Onlygoodinmath
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DNA Supercoiling

Post by Onlygoodinmath » Fri Oct 09, 2009 3:02 am

A question on a quiz read:

Which of the following DNA molecules would migrate the fastest in an electric field?

A. 1000 bp linear fragment in a agarose gel
B. 1000 bp linear fragment in a 0.7% agarose gel
C. 1000 bp supercoiled plasmid in a 1% agarose gel
D. 1000 bp supercoiled plasmid in a 0.7% agarose gel
E. 1500 bp linear fragment in a 1% agarose gel

I narrowed it down to C or D, but I do not know how the concentration of the gel affects the migrating speed. Can someone explain that to me.

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canalon
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Post by canalon » Fri Oct 09, 2009 3:13 am

The agarose forms a gel a web of entangled molecules. The DNA moves within this web. The smaller it is, the easier it is to move within the matrix, as you already know, but increasing the agarose content is just like increasing the density of the web. What do you think is the effect on the speed of migration?
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

Onlygoodinmath
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Re: DNA Supercoiling

Post by Onlygoodinmath » Fri Oct 09, 2009 3:20 am

So... increasing the agarose concentration makes it harder for the DNA to travel through the gel. So then, its obviously D.

Thanks. I appreciate the help.

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JackBean
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Post by JackBean » Fri Oct 09, 2009 6:45 am

Yeah, that's right ;)
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

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