Replica Plating Method - In this method, bacteria are grown for a fixed amount of time along with a mutagen. Then the bacteria are plated on nutrient media supplemented with vitamins, amino acids, etc. This plate is used as master plate.

Replicas are made by pressing velvet covered wooden blocks against the master plate and then pressed in the same orientation onto the surface of petri plates containing fresh nutrient media supplemented with vitamins and amino acid, expect one vitamin or amino acid.