EtBr in agarose gels vs. EtBr staining later

[rmoldwin at midway.uchicago.edu]

In article <Pine.A32.3.91.950222182822.74692A-100000 at rs5.tcs.tulane.edu>, Brick 
Ayola <abrick at mailhost.tcs.tulane.edu> writes:

>
>Regarding EtBr staining of nucleic acids:
>Can one simply add EtBr to the loading dye (as with some RNA gel 
>protocols)? Or will this significantly disturb the migration of DNA 
>super-coils and such?
>
>Brick Ayola, Ph.D.
>Tulane School of Medicine

If I recall correctly, when I tried it, the EtBr migrated in the opposite 
direction as the DNA.  Also, when you add EtBr to the gel, you can see that the 
bottom of the gel is always darker than the top.  I think this is because the 
EtBr migrates upward.  The implication is that low bp bands at the bottom of 
the gel may not show up under UV light.  Am I right about this