Dr. Duncan Clark duncan at
Thu Oct 16 07:03:34 EST 1997

In article <34460921.4F5A at>, Thomas Eitinger
<thomas=eitinger at> writes
>can anybody tell me whether the lacU169 deletion in E. coli which
>comprises the region between argF and lac also affects the lacI gene? In
>other words, does strain DH5 (lacU169) alpha produce a Lac repressor?
>Thomas Eitinger <thomas=eitinger at>

It doesn't produce lacI ie pUC18 plated on Xgal (with no IPTG) gives
blue clonies. 

We use it for fidelity testing polymerases ie 4.5kb pUC containing lacI;
PCR all the way round using enzyme under test, Dpn I treat (to kill of
original template), cut and ligate unique RE site in primers and
electroporate DH5alpha and plate on Xgal, Amp. White colonies are
wildtype, blues are errors. More blues, the worse the PCR enzyme
fidelity. Count a few thousand and calculate fidelity.

The problem with being on the cutting edge is that you occasionally get 
sliced from time to time....

Duncan Clark
DNAmp Ltd.
TEl/FAX 01252376288

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