Read the Passage carefully and answer the questions.
Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges. The first clinical gene therapy was given in 1990 to a 4-year old girl with adenosine deaminase (ADA) deficiency. This enzyme is crucial for the immune system to function. Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis of diseases. Transgenic animals that produce useful biological products can be created by the introduction of the portion of DNA (or genes) which codes for a particular product such as human protein (α-1-antitrypsin) used to treat emphysema. Biopiracy is the term used to refer to the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned without compensatory payment.
In early diagnosis of disease, the principle of antigen-antibody interaction operates in-
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Enzyme Linked Immuno Sorbent Assay
In ELISA, the antigen of a pathogen binds to its specific antibody, and an enzyme linked to the reaction gives a colour that can be measured. It can detect an infection by finding either the pathogen’s antigens or the antibodies the body has made against it.
Option (1) Computed tomography — Incorrect. CT uses X-rays to image internal organs; no antigen or antibody is involved.
Option (2) Recombinant DNA technology — Incorrect. In diagnosis it uses DNA probes that pair with complementary DNA, not antigen-antibody binding.
Option (3) Polymerase Chain Reaction — Incorrect. PCR amplifies the pathogen’s nucleic acid; it works by copying DNA.
Option (4) Enzyme Linked Immuno Sorbent Assay — Correct. ELISA, the enzyme linked immuno-sorbent assay, works on the principle of antigen-antibody interaction. It is used in the early diagnosis of diseases by detecting the pathogen’s antigens or the antibodies against them.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Molecular Diagnosis – “… Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.”
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.”