question_answer 23)

  An antibiotic resistance gene in a vector usually helps in the selection of (a) competent cells         (b) transformed cells      (c) recombinant cells      (d) None of these

Answer:

                  (b) Selectable markers help in identifying and eliminating non-transformants and selectively permitting the growth of the transformants. The normal E. coli cells do not carry resistance against any of these antibiotics. Competant bacterial cells are made capable to take foreign DNA with chemical treatment, e.g., calcium chloride. Note In process of transformation, a piece of DNA is introduced in a host bacterium.