What do you understand by the term selectable marker?
Selectable marker: A marker is a gene which helps in selecting those host cells which contain the vector (transformant) and eliminating the non-transformants. It selectively permits the growth of transformants. Common selectable markers for E. coli include the genes encoding resistance to antibiotics such as ampicillin. chloramphenicol tetracycline and kanamycin or the gene for (i-galactosidase which can be identified by a colour reaction. Normal E.Coli do not carry resistance against any of these antibodies.
