1. What does PCR stand for in molecular biology?
A. Protein Chain Reaction
B. Polymerase Chain Reaction
C. Phosphate Chain Reaction
D. Polypeptide Chain Reaction
Answer: B. Polymerase Chain Reaction
Explanation: PCR amplifies specific DNA sequences using a heat-stable DNA polymerase, primers, and thermal cycling.\n\n—
2. Which enzyme is crucial for PCR?
A. RNA polymerase
B. Reverse transcriptase
C. DNA ligase
D. Taq polymerase
Answer: D. Taq polymerase
Explanation: Taq polymerase, derived from Thermus aquaticus, is heat-resistant, making it ideal for the high temperatures used in PCR.\n\n—
3. What is the main role of primers in PCR?
A. Degrade DNA strands
B. Provide starting points for DNA synthesis
C. Terminate DNA synthesis
D. Stabilize the DNA polymerase
Answer: B. Provide starting points for DNA synthesis
Explanation: Primers are short DNA sequences that anneal to target regions, guiding DNA polymerase during amplification.\n\n—
4. What is the typical temperature for the denaturation step in PCR?
A. 50-60\u00b0C
B. 72\u00b0C
C. 90-95\u00b0C
D. 37\u00b0C
Answer: C. 90-95\u00b0C
Explanation: High temperatures are used to separate double-stranded DNA into single strands.\n\n—
5. Which of the following is NOT an application of PCR?
A. DNA fingerprinting
B. RNA sequencing
C. Disease diagnosis
D. Cloning specific genes
Answer: B. RNA sequencing
Explanation: RNA sequencing involves sequencing RNA, while PCR amplifies DNA or complementary DNA (cDNA).\n\n—
6. What is the purpose of the annealing step in PCR?
A. DNA strand separation
B. Primer binding to target DNA
C. DNA elongation
D. RNA synthesis
Answer: B. Primer binding to target DNA
Explanation: Annealing involves primers attaching to complementary DNA sequences, typically at 50-60\u00b0C.\n\n—
7. Real-time PCR (qPCR) is primarily used for:
A. Amplifying DNA fragments
B. Quantifying DNA in real time
C. Isolating RNA
D. Visualizing proteins
Answer: B. Quantifying DNA in real time
Explanation: qPCR measures DNA amplification in real time using fluorescence.\n\n—
8. Which modification of PCR is used to amplify RNA?
A. Real-time PCR
B. Nested PCR
C. Reverse transcription PCR (RT-PCR)
D. Multiplex PCR
Answer: C. Reverse transcription PCR (RT-PCR)
Explanation: RT-PCR converts RNA into cDNA before amplification.\n\n—
9. PCR can be used in forensic science for:
A. Identifying blood groups
B. Analyzing DNA from crime scenes
C. Detecting viruses
D. Synthesizing proteins
Answer: B. Analyzing DNA from crime scenes
Explanation: PCR amplifies small amounts of DNA from crime scenes for identification.\n\n—
10. What is the elongation temperature in PCR?
A. 37\u00b0C
B. 60\u00b0C
C. 72\u00b0C
D. 95\u00b0C
Answer: C. 72\u00b0C
Explanation: 72\u00b0C is the optimal temperature for Taq polymerase to synthesize DNA.\n\n—
11. What is multiplex PCR?
A. Amplification of single DNA sequence
B. Amplification of multiple DNA sequences simultaneously
C. PCR using multiple enzymes
D. PCR without primers
Answer: B. Amplification of multiple DNA sequences simultaneously
Explanation: Multiplex PCR uses multiple primer pairs to amplify several DNA regions at once.\n\n—
12. Nested PCR is used to:
A. Avoid contamination
B. Amplify short DNA fragments
C. Increase specificity of amplification
D. Measure RNA levels
Answer: C. Increase specificity of amplification
Explanation: Nested PCR uses two sets of primers to reduce non-specific amplification.\n\n—
13. Which application of PCR helps detect genetic mutations?
A. DNA sequencing
B. RT-PCR
C. Allele-specific PCR
D. RAPD PCR
Answer: C. Allele-specific PCR
Explanation: Allele-specific PCR identifies specific mutations in DNA sequences.\n\n—
14. What is RAPD-PCR?
A. Random Amplified Polymorphic DNA PCR
B. Rapid Amplification of DNA PCR
C. Reliable Amplification Protocol PCR
D. Restricted Amplified DNA PCR
Answer: A. Random Amplified Polymorphic DNA PCR
Explanation: RAPD-PCR identifies genetic polymorphisms without prior knowledge of DNA sequences.\n\n—
15. Which is a diagnostic application of PCR?
A. Imaging tumors
B. Detecting infectious pathogens
C. Measuring blood pressure
D. Observing protein folding
Answer: B. Detecting infectious pathogens
Explanation: PCR detects pathogen-specific DNA in samples, aiding in early diagnosis.\n\n—
16. How does digital PCR differ from traditional PCR?
A. It does not use primers.
B. It quantifies DNA absolutely.
C. It amplifies RNA.
D. It does not require thermal cycling.
Answer: B. It quantifies DNA absolutely.
Explanation: Digital PCR partitions DNA into many small reactions for precise quantification.\n\n—
17. PCR is used in phylogenetics to:
A. Study fossil records
B. Analyze DNA sequences to determine evolutionary relationships
C. Synthesize proteins
D. Detect viruses
Answer: B. Analyze DNA sequences to determine evolutionary relationships
Explanation: PCR amplifies ancient or rare DNA for evolutionary studies.\n\n—
18. What is a key advantage of PCR in genetic engineering?
A. Protein analysis
B. Amplification of specific genes for cloning
C. Measurement of enzyme activity
D. Observation of cell division
Answer: B. Amplification of specific genes for cloning
Explanation: PCR isolates and amplifies desired genes for insertion into vectors.\n\n—
19. Which disease detection involves PCR?
A. Tuberculosis
B. HIV
C. COVID-19
D. All of the above
Answer: D. All of the above
Explanation: PCR detects pathogens like Mycobacterium tuberculosis, HIV, and SARS-CoV-2 by amplifying specific DNA/RNA sequences.\n\n—
20. What is the main advantage of PCR in personalized medicine?
A. Amplification of viral proteins
B. Identification of genetic variations for targeted therapies
C. Cloning DNA into bacteria
D. Analysis of blood pressure
Answer: B. Identification of genetic variations for targeted therapies
Explanation: PCR detects patient-specific genetic markers, guiding individualized treatment plans.
