What are the two ways that we know cell clones carry recombinant plasmids?
One way to test for the presence of recombinant plasmids in group of cells is to test for certain traits that are caused by the genes be present on the desired recombinant plasmid. For example, if the desired recombinant plasmid contains an operon that allows for the breakdown of lactose and a gene that provides antibiotic resistance to penicillin, both of which originated from different DNA fragments and which should not interrupt each other, then one can put cells on a culture that contains lactose as a food source and penicillin as an antibiotic. Only cells with the desired plasmid, and thus both traits, will be able to survive and form colonies because the cells require the ability to both metabolize lactose and resist penicillin, traits that only a recombinant could have. Thus, the cells that thrive on the culture carry the desired recombinant plasmids. Another method is to remove copies of plasmids from the cells and sequence them, looking for sequences that match the sequence of
