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appearance of "clean" DNA?

benedik benedik at uh.edu
Fri Jan 5 10:27:27 EST 2001

DNA is definitely viscous. This is because it is a long chain polymer which
is what makes it viscous. If you shear it into smaller bits (such as by
sonication) the viscosity will be reduced. You can also prove this by adding
a little DNase and watch the viscosity go away.

Now, when you extract DNA from some bacteria and especially from plants you
also tend to get a lot of polysaccharides which might also contribute to the
viscosity. But it is mostly the DNA.

in article 9338a4$e88$1 at nnrp1.deja.com, mwcrepeau at my-deja.com at
mwcrepeau at my-deja.com wrote on 1/4/01 7:33 PM:

> What does clean genomic DNA look like?  It should, of course, form a
> clear, colorless solution when dissolved in TE buffer, but what about
> viscosity?  I remember a graduate student looking at one of my first
> plant DNA preparations when I was un undergrad and telling me that
> there was a good yield because the prep was very viscous.
> Later, someone else told me that DNA itself is not viscous in solution
> and that any viscosity is due to contaminants.  That seems reasonable,
> but it has also been my experience that the viscosity is almost
> impossible to eliminate, even with several additional phenol/chloroform
> extractions and/or ethanol precipitations.
> What is responsible for the viscosity that is typical of plant genomic
> DNA preps?  Moreover, if I could get my genomic DNA completely clean,
> so that nothing was left but the nucleic acid itself, what would it
> look like in solution?  And what would it look like as an ethanol
> precipitate?  Would it appear as the white cloud that I am accustomed
> to seeing, or is the white color due to bound protein and/or other
> contaminants?
> Perhaps this is just a theoretical question, since it may not be
> possible to obtain completely clean genomic DNA, but I'm still curious
> what people think about it.
> Marc Crepeau
> <mwcrepeau at hotmail.com>
> Sent via Deja.com
> http://www.deja.com/

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