blue/white selection problem

Rodney Earl Pettway earlpettway at
Tue May 16 11:29:43 EST 2000

Thanks for the info.

Have a great day!!!!!!!!

"Frank O. Fackelmayer" wrote:

> One possible reason could be overdigestion of the vector, resulting in
> damaged ends. These could still be ligated in some cases, leading to
> white colonies. As you say the vector is from a kit, it is possible that
> the DNA has been damaged by multiple freeze-thaws.
> Anyway, I assume there are not only white but also blue colonies. Check
> some of those to see if they might have the insert. Blue-white selection
> is sometimes misleading. Especially with short inserts it is quite
> common to see blue or slightly blueish colonies that HAVE the insert,
> while white colonies haven´t. I´ve had clonings where the blueish
> colonies had the insert, but neither the blue nor the white ones. Then I
> had positive clones that where perfectly blue...
> Well, as a consequence, I´m hardly doing blue-white selection after all nowadays.
> Frank
> > I am using blue/white selection to choose colonies with my insert.
> > Unfortunately, my white colonies don't have inserts.  What could be
> > causing this.
> >
> > Rodney Earl Pettway
> > USDA-ARS Cereal Disease Lab
> > University of Minnesota
> > St. Paul, MN., 55108

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