Molecular diagnosis - PCR and ELISA — practice questions

Question 1 · difficulty L1 · recall

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

Question 2 · difficulty L2 · understanding

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

Question 3 · difficulty L2 · understanding

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

Question 4 · difficulty L3 · application

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

Question 5 · difficulty L4 · analysis

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

Question 6 · difficulty L5 · analysis

A genetic disorder is caused by a known DNA mutation present in very few cells in a sample. Why might PCR be included in the diagnostic workflow?

• A. It guarantees the mutation causes symptoms
• B. It can change the mutation back to normal
• C. It measures enzyme activity without DNA
• D. It amplifies the mutation-containing region