blue colonies

Edward Wang ez022056 at
Tue Apr 25 13:16:44 EST 1995

I am currently doing PCR cloning using the Promega pGem-T system.  
Everything was working fine, and I was getting several hundred : 5 White 
to blue ratio, using Stratagene's super competent (10^9 efficiency) XL1 
Blue cells.  Because of the high cost, I switched to Promega's JM109 
(10^8 efficiency).  Now, my plates have lots of blue colonies : very few 
white colonies.  Does anyone know any explaination for this?
Also, we are trying to od Nrothern blots with probes made from 
differentialy displaying fragments (DD-RTPCR), but so far with no luck 
(nothing shoing on the blot).  Has anyone else had any similar problems, 
and perhaps even the solution to the problems?  Thanks in advance.

Edward H. Wang                 *
Staff Resch. Assc.             *
Dept. Internal Med. -Nephrology*
UC Davis                       *

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