Replica plating Make three replica 1. Invert master plate; 2. Invert second plate plates. Incubate to pressing against velvet replica plate); pressing allow penicillin surface leaves an imprint against velvet surface 107 colonies of resistant colonies of colonies. Save plate icks up colony imprint. penicillin-sensitive bacteria to grow s Master plate Penicillin Master plate Penicllin No penicillin in medium No penicillin in medium In medium 3. Incubate Velvet PenicillIn in medium 4. Only penicillin-resistant colonies grow. Compare position of colonies on original plate in medium Penicillin-resistant s= penicillin-sensitive bacteria colonies grow in the R= penicillin-resistant bacteria same position on all three plates