Band tapering on sequencing gels: why?

Laurentiu COCEA cocea at
Thu Jun 8 14:00:43 EST 1995

Hi- I do sequencing and use gradient acrylamide gels quite often and 
can't understant something:

On some gels (most of them, actually), the DNA bands are tapered at
the bottom end. This phenomenon starts right after migration start,
and the only affected region is the one at the bottom. You can see
this on the gels (the blue bands "shrink") and you can also see it when
you develop your film, i. e. the radioactive bands have the same 
tapered pattern. I read something about buffers having to be exactly
identical (the TBE in the gel and the one that you add "at the top" and
"the bottom" of the apparatus in order to have electric contacts at the
ends of the gel); could nonidentical composition be the explanation?
However, I don't think so - it works beautifully for some gels and 
everybody in the lab uses the same solutions.

Thanks alot for any hint.

Laurentiu COCEA (cocea at


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