Help explain my DNA bands smearing

[Rafael Maldonado]

On 25 Sep 1995, jene wrote:

> Hello, recently I did a gel electrophoresis on genomic DNA isolated from 
> Arabidopsis. The samples were restricted with MluI, EcoRI and SAU3A.
> I expected to see distinct bands of DNA but ended up with smears in all 
> my lanes. 

Why did you expect that? I would expect a big smear.

A smear is the result of many bands. With that digestion, you get many 
different bands, and the range of size is almost continous: there are 
many bands, each one very close to the next one. That because you don't 
see any band.

Most of the enzymes give a smear when you digest chromosomal DNA with 
them. Except, of course, those that cut very rarely in your genome. 
That's the theory of the pulsed filed electrophoresis.

	-Rafa

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