Antibiotic resistant markers

Antibiotic-resistance markers offer the simplest possible screening logic: build the resistance gene into the vector itself, then grow the transformed cell population on a medium laced with that specific antibiotic. Any cell that actually took up the vector - and with it, the resistance gene - survives and grows into a visible colony; every cell that did not take up the vector has no protection against the antibiotic and simply dies. Common markers used this way include resistance to ampicillin, chloramphenicol, tetracycline and kanamycin. This approach is genuinely useful precisely because it requires no further testing or visual interpretation: growth on the selective plate is itself the read-out, distinguishing transformed cells from untransformed ones in one single step, though on its own it cannot distinguish a true recombi …