Question

How would you change the medium (original medium is in LB broth) used to determine if the trp+ gene had been transferred? (E. coli CSH 121 and 0.1 ml of E. coli CSH 125 was added to 1 ml of of LB broth. The tube was then incubated at 37oC for 45 minutes. The cell mixture was grown on a LB + streptomycin + tetracycline plate.)

Answer 1

To determine whether trp+ gene had been transferred or not grow the organism on minimal media + streptomycin + tetracycline plate ( it will only work when the organism had only one mutation i.e trp mutation if it is unable to synthesize other Biomolecules as well like histidine, threonine and proline then minimal media should be supplied with all these Biomolecules for this you have to first test whether the organisms is deficient for one Biomolecules or multiple Biomolecules).