Question 1

Which of the following is NOT an essential ingredient for a standard PCR reaction?

Accepted Answer

RNA polymerase

Question 2

Why is Taq DNA polymerase used in PCR instead of other DNA polymerases?

Accepted Answer

It is resistant to high temperatures required for denaturation

Question 3

During the denaturation step of PCR, what happens to the DNA?

Accepted Answer

Double-stranded DNA melts into single strands

Question 4

What is the primary purpose of the buffer in a PCR reaction?

Accepted Answer

To maintain the pH for optimal enzyme activity

Question 5

If a PCR reaction fails to produce any product, which of the following is LEAST likely to be the cause?

Accepted Answer

Use of Taq polymerase

Question 6

Which equation best describes the exponential amplification of DNA during PCR, assuming perfect efficiency?

Accepted Answer

$$2^n$$

Question 7

What is the role of primers in PCR?

Accepted Answer

They anneal to flanking sequences and initiate DNA synthesis

Question 8

Which step in the PCR cycle involves the formation of hydrogen bonds between primers and the template DNA?

Accepted Answer

Annealing

Question 9

Why do DNA fragments migrate through an agarose gel during electrophoresis?

Accepted Answer

Because DNA fragments are separated based on their length and negative charge

Question 10

A researcher wants to amplify a gene from a thermophilic bacterium. Which DNA polymerase should they use for optimal PCR performance?

Accepted Answer

Taq DNA polymerase from Thermus aquaticus

Question 11

Which of the following is a real-world application of PCR?

Accepted Answer

Forensic analysis

Question 12

What is the function of Mg2+ in a PCR reaction?

Accepted Answer

Acts as a cofactor for DNA polymerase

Question 13

During the extension step of PCR, in which direction does DNA polymerase synthesize the new strand?

Accepted Answer

5' to 3'

Question 14

A gel electrophoresis result shows two PCR samples with bands at the same position as the ladder. What does this indicate?

Accepted Answer

The samples contain DNA fragments of the same length as the ladder standard

Question 15

Which of the following best describes the process of hybridization in PCR?

Accepted Answer

Combining two complementary single-stranded DNA molecules to form a double-stranded molecule

Question 16

If a primer does not exactly match the template DNA, what is the most likely outcome during the annealing step?

Accepted Answer

The primer will not bind efficiently, reducing PCR yield

Question 17

Which of the following is NOT a use of PCR in molecular biology?

Accepted Answer

Protein purification

Question 18

A scientist runs 30 cycles of PCR. Assuming perfect efficiency, how many copies of the target DNA will be produced from a single template?

Accepted Answer

$$2^{30}$$

Question 19

Which step in PCR is most sensitive to the melting temperature of the primers?

Accepted Answer

Annealing

Question 20

What is the main reason longer DNA fragments move slower than shorter fragments during agarose gel electrophoresis?

Accepted Answer

Longer fragments encounter more resistance in the gel matrix

Polymerase Chain Reaction (PCR): Principles, Process, and Applications

Study Guide - Practice Questions