An antibiotic resistance gene in a vector usually helps in the selection of

1. Competent bacterial cells                             
2. Transformed bacterial cells
3. Recombinant bacterial cells                           
4. None of the above

(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.