“PCR Quiz Part 1 – Basics of Polymerase Chain Reaction (10 MCQs)”

Attempt all 10 questions. Click Submit to check your score and correct answers.

1. The melting temperature (Tm) of a DNA duplex depends on its GC content. Which formula is commonly used for short primers?

a) Tm = 2(A+T) + 4(G+C)
b) Tm = (A+T+G+C) × 2
c) Tm = 4(A+T) + 2(G+C)
d) Tm = (G+C)/(A+T) × 100

2. A PCR reaction starts with 100 copies of DNA. After 20 cycles (100% efficiency), how many copies will be produced?

a) 1.05 × 10⁶
b) 1.05 × 10⁸
c) 1.05 × 10⁷
d) 1.05 × 10⁹

3. In PCR, the denaturation step is usually carried out at:

a) 37°C
b) 55°C
c) 72°C
d) 94°C

4. Which DNA polymerase is commonly used in standard PCR?

a) DNA Pol I
b) DNA Pol III
c) Taq polymerase
d) Reverse transcriptase

5. Which of the following is NOT essential for PCR?

a) DNA template
b) dNTPs
c) Restriction enzyme
d) Primers

6. What is the typical length of primers used in PCR?

a) 6–10 bases
b) 18–24 bases
c) 40–60 bases
d) >100 bases

7. If extension rate of Taq polymerase is ~1000 bases/min, how long is required to amplify a 2 kb fragment?

a) 30 sec
b) 1 min
c) 2 min
d) 3 min

8. The exponential phase of PCR continues until:

a) Primers run out
b) dNTPs run out
c) Polymerase loses activity
d) All of the above

9. Hot-start PCR is mainly used to:

a) Increase DNA denaturation
b) Prevent nonspecific amplification
c) Increase speed of polymerase
d) Replace annealing step

10. Which of the following is a limitation of Taq polymerase?

a) Low fidelity (no proofreading)
b) Works only at 25°C
c) Cannot use primers
d) Requires Mg²⁺ ions

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