pBR322 is one of the first known cloning vectors to be used for molecular cloning. Similarly to pUC18, it has an ampicillin gene but in contrast, it has another gene known as tetracycline. These two genes confer resistance to their respective antibiotic, but suppose a foreign DNA fragment was introduced into the tetracycline gene. Would the tetracycline gene still be functional? How could you determine recombinant clones from non-recombinant clones?