In our experience overlapping lanes at the start of a gel that gradually
separate are nearly always related to salt, usually leftover from sample
cleanup.
Salt effected samples will often be "blobby" and the gel front will be
bowed to the right or left.
The problem seems to get a lot worse when the time gap between loading
staggered lanes is over 5 minutes, rather than the normal 2-3.
How are you cleaning up you samples?
Most of our users are using the new isopropanol precipitation rather than
the old ethanol/salt pptte and now we have a lot less problems with
overlapping lanes than we used to.
>I wonder if it has to do with the total amount of DNA on the gel.
> Has anyone tried to "over load"a gel to see what happens?
I get overloaded samples all the time and have not noticed much effect on
tracking .
I had one user who gave me samples that had average signal strengths of
over 3500 (gain of 4 on a 377) and they ran straight.
Macky Edmundson - Queensland Institute of Medical Research
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