Early Diagnosis Techniques in Biotechnology — NEET Biology

Correct answer: B — S1, S2 and S4 are correct

The core concept here revolves around various molecular diagnostic techniques used in medicine, specifically PCR, ELISA, and autoradiography, as well as gene therapy for genetic disorders. S1: Correct. NCERT states, 'However, very low concentration of a bacteria or virus (at a time when the symptoms of the disease are not yet visible) can be detected by amplification of their nucleic acid by PCR.' S2: Correct. NCERT states, '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.' S3: Incorrect. NCERT states, 'The clone having the mutated gene will hence not appear on the photographic film, because the probe will not have complementarity with the mutated gene.' The statement incorrectly claims the probe forms a stable hybrid with the mutated sequence. S4: Correct. NCERT states, 'PCR is now routinely used to detect HIV in suspected AIDS patients. It is being used to detect mutations in genes in suspected cancer patients too. It is a powerful techqnique to identify many other genetic disorders.' S5: Incorrect. NCERT states regarding ADA deficiency treatments, 'But the problem with both of these approaches that they are not completely curative.' (referring to bone marrow transplantation and enzyme replacement therapy). Gene therapy at early embryonic stages *could be* a permanent cure, contradicting the claim that gene therapy offers only temporary solutions. Therefore, statements S1, S2, and S4 are correct.