using MacConkey agar for "red/white" selection

Creg Darby cdarby at
Sat May 7 23:55:35 EST 1994

vam2 at (Viraj) writes:

>I wanted to order some MacConkey agar for red/white color selection of
>recombinants, but noticed there are several different kinds that one
>can order from Difco.

At risk of being called a nitpicker, may I point out that what Viraj 
describes is not a "selection" but a "screen." In a selection, you kill 
what you don't want, e.g. use ampicillin to kill non-plasmid-bearing 
cells. If you do a red/white (or blue/white) protocol in which everything 
survives but there is an observable difference, that's a screen.

Creg Darby
cdarby at
Department of Genetics SK-50, University of Washington, Seattle, WA 98195
voice: 206-543-9446   fax: 206-543-0754

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