Final answer:
Antibiotic resistance in recombinant bacteria is conferred by a gene encoded on the plasmid. This allows scientists to select for the successfully transformed bacteria when they are cultured on media containing the antibiotic.
Step-by-step explanation:
Recombinant bacteria are selected for antibiotic resistance because they carry a plasmid encoded with the antibiotic resistance gene. During the process of genetic engineering, this gene is integrated into the plasmid, which is then introduced into the bacterial cells. When the bacteria are grown on a medium containing the specific antibiotic, only those that have taken up the plasmid with the resistance gene can survive. This selection process allows scientists to identify and cultivate the bacteria that have been successfully transformed with recombinant DNA.
The resistance itself is not activated by the recombination event or by exposure to the antibiotic; it is a feature of the plasmid that, when introduced into bacterial cells, provides resistance. The process of molecular cloning includes steps like transformation, culturing on selective media, and distinguishing between recombinant and non-recombinant bacteria, making use of the antibiotic resistance marker.