FISH probe random prime or nick translate

W R Bennett bspwrb at
Tue Mar 18 13:37:43 EST 1997

In the referenced article, tyr-2 at (Karl Fischer) writes:
>In article <332D72CD.3B3E at>, pgold at wrote:
>> I believe that the nick translation is used so that a probe of about 500
>> bp can be generated.
>From the history books (ie. mid-80s)
>Average size of fragments generated by nick translation of pBR322 was
>500-1000 bases as seen following alkaline agarose electrophoresis.
Well, this is my point, really.  The dogma is that nick translation
generates longer probes than random priming, but... so what?  Random
priming generally works better on Southerns, it's believed that the
"networking effect" enhances the signal with the shorter random primed
probes, and you pre-anneal FISH probes with Cot-1 DNA to remove shorter
fragments which cross-react with other regions of the genome, so why not? 
Is there an over-riding reason why long probes are better for FISH? 

Just curious,

Bill Bennett
Developmental Biology Unit,
School of Biology and Biochemistry
University of Bath

bspwrb at

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