gt11 blue/white plaques?

Jim Mensch jm68 at
Fri Jan 27 13:06:23 EST 1995

I have a lambda gt11 cDNA library which I obtained from ATCC.  In the
course of titering the library, I added X-gal and IPTG to the top agar
of one plating, expecting to see a large majority of white (colorless)
plaques indicating phage carring an insert in the lacZ portion of the
gt11 construct.  In fact, I saw about 80% (eyeball estimate, too many
plaques to count) blue:20% clear.  Can anyone confirm my speculation 
that since the insert (EcoRI) site is near the 3' end of the lacZ
coding region many inserts do not interfere with the complementation
of this lacZ product with the defective host B-galactosidase?  
Thanks!  J. Mensch
Jim Mensch <j-mensch at> 

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