blue colonies-no Xgal

Michael H. Bracey mbracey at
Fri Jun 28 00:20:16 EST 1996

I recently cloned some PCR products into InVitrogen's tailed vector and 
transformed the ligation products into their SureShot Top10 cells which 
are supposed to have a lacIq repressor.  In the *absence* of both IPTG 
and X-gal, I got back about 50% blue colonies.  Is there a trivial 
explanation for this that I'm overlooking?  Where is the blue coming 

Emailed replies are especially welcome.

mbracey at

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