Nutritional mutants replica plating method The photograph on the left shows the master plate The colonies not appearing on the replica plate are marked with an X The replica plate lacked one nutrient (leucine) present in the master plate Therefore,the colonies marked with an X are leucine auxotrophs Nutritional mutants replica plating method • The photograph on the left shows the master plate • The colonies not appearing on the replica plate are marked with an X • The replica plate lacked one nutrient (leucine) present in the master plate • Therefore, the colonies marked with an X are leucine auxotrophs