A single stranded DNA or RNA tagged with a radioactive probe is allowed to hybridize to its complementary DNA in a clone of cells followed by detection using ___________.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Autoradiography
Option (1) Polymerase chain reaction — Incorrect. PCR makes many copies of a piece of DNA, so that a very small amount of a pathogen’s DNA can be found. It does not detect where a radioactive probe has bound.
Option (2) ELISA — Incorrect. ELISA (enzyme linked immuno-sorbent assay) works on antigen-antibody interaction. It detects the antigens of a pathogen or the antibodies made against it; no DNA probe is used.
Option (3) Autoradiography — Correct. A probe is a short piece of DNA or RNA carrying a radioactive label. Where it binds to its complementary DNA, its radiation darkens a photographic film, so the clone that carries the gene shows up on the film.
Option (4) Gel electrophoresis — Incorrect. It separates DNA fragments by size as they move through an agarose gel. The bands are seen after staining with ethidium bromide under UV light.
NCERT Extract:
Molecular Diagnosis – …
