Replica plating is a biology lab technique
used mainly for identifying and selecting mutant colonies
of a microorganism
when the mutant
can only be selected against
(rather than selected for
The microorganisms are cultured on a plate of agar. Then a replica plate is made by blotting the microbial colonies with a membrane and blotting the membrane on another agar plate. This results in all colonies from the first plate being in identical locations on the second plate. The second plate either contains some substance which kills off microbes possessing the mutation of interest, or the agar medium lacks a substance necessary for the mutants to grow. Later, it is determined which colonies on the first plate failed to grow on the second plate, thus identifying the mutants microbes of interest to the researcher.
The information in this writeup was taken from the science dictionary at http://biotech.icmb.utexas.edu/; I oversaw the development of the dictionary (the website was mothballed in 1998) and I believe I wrote the entry this is based on.