Why probe hybridizes to vector?

Mic Chaudoir mic at nwu.edu
Mon Jul 10 15:51:47 EST 1995


In article <biolc4-020795165223 at mac-918.sr2-building.uh.edu>,
biolc4 at jetson.uh.edu (Wenfu) wrote:

> When I was using isolated DNA fragment( I am sure no any vector sequence in
> it)
> to probe digested plasmids, I found my probe hybridizes to the vector.
> This kind of thing happen to me several times when I was doing the similar
> thing. Although it did not matter for my results, I am really curious 
> about the reasons for.
> Any idea would be appreciated

Whenever you gel purify something, a residual amount of other DNA in the
mixture comes along.  For example, if one cuts out a single band from PKS,
and gel purifies it, some PKS comes along too.  Usually the amount is so
small that it makes no difference.  However, the only way to completely
eliminate it is multiple rounds of gel purification (actually, the
contamination will still be there, just too small to be detectable by any
means).  Anyway, practically, I find that this problem is only worth
mentioning when gel purifying from an overloaded gel.  If you overload the
gel, you will still get seperation, but a larger amount of the plasmid
will be carried along.  gel purify smaller amounts at a time, or use
larger gels, and you should solve the problem.

-- 
Name:Mic Chaudoir    
E-mail:mic at nwu.edu
WWW:http://pubweb.acns.nwu.edu/~chaudoir/micpage.html
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