Smiling bands within lanes of an agarose gel?

Guy A. Hoelzer hoelzer at
Tue Nov 18 15:19:12 EST 1997

What causes smiling bands within lanes of agarose gels?  I have seen this
before, but never really understood the cause.  In this case, 5 ug of
total genomic DNA from a bird was cut with a restriction enzyme and run on
a 1% agarose gel at 30 volts overnight.  There was ethidium bromide in
both the gel and the running buffer.  This is a multilocus fingerprinting
project, so the resulting gel was Southern blotted and probed with an AP
conjugated repeat oligo.  There appears to be a positive relationship
between the amount of DNA in a lane and the degree of band smiling.

Our current best guess is that the band smiling is caused either by
running with EtBr, or by insufficient purification of the genomic DNA,
which might have caused spurious cutting by the restriction enzyme.  What
do you think?

Guy Hoelzer                              e-mail:  hoelzer at
Department of Biology                    phone:   702-784-4860
University of Nevada Reno                fax:     702-784-1302
Reno, NV  89557

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