Now a days it is possible to detect the mutated gene causing cancer by allowing radioactive probe to hybridise its complementary DNA in a clone of cells, followed by its detection using autoradiography because:
Answer: (A) mutated gene does not appear on a Photographic film as the probe has no complementarity with it. Answer: (A) mutated gene does not appear on a Photographic film as the probe has no complementarity with it Solution: The radioactive probe is designed to be complementary to the normal gene sequence.
- A.mutated gene does not appear on a Photographic film as the probe has no complementarity with it✓
- B.mutated gene does not appear on Photographic film as the probe has complementarity with it
- C.mutated gene partially appears on a photographic film
- D.mutated gene completely and clearly appears on a photographic film.
Correct Answer
(A) mutated gene does not appear on a Photographic film as the probe has no complementarity with it
Solution & Explanation
Answer: (A) mutated gene does not appear on a Photographic film as the probe has no complementarity with it Solution: The radioactive probe is designed to be complementary to the normal gene sequence. Where a gene is mutated, the probe cannot base-pair (hybridise) with it because it has no complementarity, so no radioactive signal is recorded and that region does not appear on the autoradiograph/photographic film. NCERT notes that techniques of molecular biology are used to detect genes that predispose individuals to cancers; the principle of probe hybridisation followed by autoradiography is the extension reasoning. Why others are wrong: B reverses the logic (complementarity would make it appear); C and D claim it appears partially/clearly, contradicting the no-hybridisation principle. NCERT Reference: NCERT Ch7, p.141 line 46 to p.142 line 5: "Techniques of molecular biology can be applied to detect genes"