The gene encoding resistance to which antibiotic are considered useful selectable marker for E. coli.

(A) ampicillin

(B) tetracycline

(C) kanamycin

(D) penicillin

(E) chloramphenicol

Choose the correct answer from the options given below:

(A), (B), (C) and (E) only

The correct answer is Option (4) – (A), (B), (C) and (E) only

In genetic engineering, a selectable marker is a gene that confers a specific trait, such as resistance to an antibiotic, which allows researchers to identify and select cells that have successfully incorporated recombinant DNA. In this scenario, the ampicillin resistance gene present in the recombinant DNA allows the host E. coli cells to become ampicillin-resistant when they take up the recombinant DNA. Therefore, the ampicillin resistance gene functions as a selectable marker in this process.

A selectable marker in genetic engineering serves as a means to identify and distinguish cells that have successfully taken up the foreign DNA (transformants) from those that haven't (non-transformants). It also allows researchers to selectively promote the growth of the transformed cells while inhibiting the growth of non-transformed cells.

One common method is to use genes that confer resistance to antibiotics as selectable markers. E. coli cells, in their natural state, do not carry resistance against certain antibiotics like ampicillin, chloramphenicol, tetracycline, or kanamycin. Researchers engineer vectors, such as plasmids, to carry both the foreign DNA of interest and a gene that provides resistance to a specific antibiotic.