Which one of the following diagnostic techniques is based on the principle of antigen-antibody interaction?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Enzyme-linked immuno-sorbent assay
Option (1) Recombinant DNA technology — Incorrect. It means joining a gene to a vector and putting it into a host to make a product. It is not a test based on antibodies.
Option (2) Polymerase Chain Reaction — Incorrect. PCR makes many copies of a piece of DNA using primers and a heat-stable DNA polymerase. It works on DNA, not on antigens.
Option (3) Enzyme-linked immuno-sorbent assay — Correct. ELISA finds an infection by an antibody binding to its antigen, with an enzyme reaction to show where the binding has taken place.
Option (4) Gel electrophoresis — Incorrect. It separates DNA fragments by size as they move through an agarose gel.
NCERT Extract:
Molecular Diagnosis – “… ELISA is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen.”
AIDS – “… A widely used diagnostic test for AIDS is enzyme linked immuno-sorbent assay (ELISA).”