NEET-UG Biology · Class 12
Molecular diagnosis - PCR and ELISA — NEET & JEE Questions
Molecular diagnosis - PCR and ELISA is a topic in Biotechnology and its Applications, a Class 12 Biology chapter of the NEET-UG syllabus. TestBudy holds 12 published NEET-UG questions on Molecular diagnosis - PCR and ELISA, each with the marking scheme of the real paper.
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Molecular diagnosis - PCR and ELISA MCQs with solutions
10 of the 12 published questions on this topic, exactly as they appear in a test. Answers and worked solutions come with your result rather than on this page.
What is a major diagnostic advantage of PCR?
- A. It detects only proteins
- B. It measures blood pressure directly
- C. It amplifies small amounts of specific DNA
- D. It replaces every microscopic and immunological diagnostic test in all situations
What does ELISA commonly detect in a diagnostic sample?
- A. Cell size and morphology measured directly by light microscopy
- B. Chromosome number directly
- C. Only DNA fragments
- D. Specific antigens or antibodies
Why can PCR detect an infection before the pathogen becomes abundant?
- A. It amplifies pathogen-specific nucleic acid
- B. It makes the pathogen reproduce inside the tube
- C. It detects symptoms before infection
- D. It converts antibodies into DNA
PCR is especially useful in diagnosis because it can
- A. amplify a specific nucleic-acid sequence from a very small starting amount
- B. detect only proteins and no nucleic acids
- C. measure blood pressure
- D. grow pathogens without DNA
A patient sample contains a pathogen antigen but no detectable antibody response yet. Which method could still identify the antigen directly?
- A. A pedigree analysis
- B. An antigen-detecting ELISA
- C. A karyotype only
- D. A Hardy-Weinberg calculation
Which PCR component determines the boundaries of the DNA region to be amplified?
- A. Primers
- B. Lipids
- C. Antibodies
- D. Ribosomes
Why is a thermostable DNA polymerase useful in PCR?
- A. It remains functional after repeated high-temperature denaturation steps
- B. It melts the DNA template permanently
- C. It acts as an antibody
- D. It prevents primer binding
An ELISA is designed to detect antibodies against a pathogen in a patient's serum. A positive signal depends primarily on
- A. specific antigen-antibody binding coupled to an enzyme-generated readout
- B. DNA replication by a thermostable polymerase
- C. visible growth of the pathogen
- D. chromosome staining
PCR gives a positive result for a pathogen-specific sequence, while antibody ELISA is still negative. Which explanation is most plausible early in infection?
- A. ELISA always becomes positive first
- B. PCR can detect only antibodies
- C. Pathogen DNA can appear before strong antibody levels
- D. The two tests must always change at the same time
A patient has a very low concentration of pathogen DNA early in infection. Which method is most directly suited to increasing the detectable amount of that DNA?
- A. PCR
- B. ELISA without any antigen or antibody target
- C. Microscopy of chromosomes
- D. Gram staining only
Common mistakes in Molecular diagnosis - PCR and ELISA
Recorded against questions in this topic that are not shown above, so none of these points at an answer you can see on this page.
- Confusing molecular diagnosis with gene therapy.
- Treats two different diagnostic principles as if both were DNA amplification.
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