Which one of the following is not used as a selectable marker for E.coli, involved in recombinant DNA technology?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Insulin
A selectable marker is a gene on a cloning vector that helps us pick out the cells that have taken up the vector (transformants) and get rid of those that have not (non-transformants). In E. coli, the genes that give resistance to antibiotics are used for this. Only a cell carrying the vector can grow on a medium that has the antibiotic in it.
(1) Insulin — Not a selectable marker. Insulin is a hormone that controls blood sugar. It is a product that can be made by recombinant DNA technology, but it is not an antibiotic, and no gene for it is used to select transformed E. coli.
(2) Kanamycin — A selectable marker. The gene for kanamycin resistance lets only the transformed cells grow on a medium with kanamycin.
(3) Chloramphenicol — A selectable marker. Chloramphenicol resistance is used in the same way.
(4) Ampicillin — A selectable marker. The vector pBR322, for example, carries the ampicillin resistance gene (ampR).
NCERT Extract:
Cloning Vectors – …
