southern size standards

Brian P Higgins via (by higginsb78 from
Wed Jun 25 23:24:02 EST 2008

Does the ladder HAVE to be on the membrane?  Most folks take a quick pic
under UV with a ruler next to the gel, then mark the exact location of the
standards (how far from the well did each band run, for example).  Then you
just measure it out on the film after your exposure.  Works pretty well.

On Wed, Jun 25, 2008 at 3:38 PM, Ed Siefker <ebs15242 from> wrote:

> I'm looking for a DNA size standard I can use with southern blots.  I don't
> want to deal with radioactive gel apparatus, so I don't want to end label
> my ladder before I run the gel.  The ideal solution would be something dyed
> so I could see with the naked eye on the membrane, and mark the sizes with
> radioactive ink.  Is there something like this available?
> Here's an idea, I can see the DNA ladder in my gel under UV.  Could I
> inject
> a small amount of P32 into each size standard, and then transfer so the
> size
> standards would be visible on the membrane?
> I've seen protocols for making size standards from lambda DNA, but these
> require probing with lambda DNA.  If I do this, would I include the lambda
> probe in the hybridization with my probe?  Do I need to reprobe with the
> lambda probe?
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