Question 1

Which of the following is the primary reason Taq DNA polymerase is used in PCR instead of other DNA polymerases?

Accepted Answer

It is thermostable and can withstand the high temperatures required for denaturation.

Question 2

During the PCR process, what is the purpose of the denaturation step?

Accepted Answer

To separate the double-stranded DNA into single strands by breaking hydrogen bonds.

Question 3

If a PCR reaction is set up with primers that do not flank the target DNA sequence, what is the most likely outcome?

Accepted Answer

No amplification will occur because the primers do not provide a starting point for Taq polymerase.

Question 4

Which equation best describes the theoretical number of DNA copies produced after $$n$$ cycles of PCR, starting from a single DNA molecule?

Accepted Answer

$$2^n$$

Question 5

Why is the annealing temperature in PCR typically set between 54–56°C?

Accepted Answer

It allows primers to bind specifically to their complementary sequences without non-specific binding.

Question 6

Which of the following is NOT a component required for a standard PCR reaction?

Accepted Answer

RNA polymerase

Question 7

In PCR, what is the role of the buffer solution?

Accepted Answer

To maintain optimal chemical conditions for enzyme activity and DNA stability.

Question 8

A forensic scientist needs to amplify DNA from a single hair follicle found at a crime scene. Which property of PCR makes this possible?

Accepted Answer

PCR can produce billions of copies from a minute amount of starting DNA.

Question 9

Which step in PCR involves the synthesis of new DNA strands by Taq polymerase?

Accepted Answer

Extension/Elongation

Question 10

A researcher designs a primer with a high GC content. What effect will this have on the annealing temperature?

Accepted Answer

It will increase the annealing temperature due to stronger hydrogen bonding.

Question 11

Which of the following best explains why PCR is considered an 'in vitro' technique?

Accepted Answer

It is performed outside living organisms, in a controlled laboratory environment.

Question 12

In a PCR-based paternity test, which genetic markers are typically analyzed to determine biological relationships?

Accepted Answer

Short tandem repeats (STRs)

Question 13

Which of the following medical applications of PCR is most relevant for detecting infectious diseases?

Accepted Answer

Amplifying pathogen-specific DNA sequences from patient samples

Question 14

What is the main difference between genomic DNA and cDNA in the context of PCR?

Accepted Answer

cDNA is synthesized from mRNA and represents only expressed genes, while genomic DNA contains all genetic material including introns.

Question 15

During the extension step of PCR, which chemical group on the primer is essential for Taq polymerase to add new nucleotides?

Accepted Answer

3'-hydroxyl (3'-OH) group

Question 16

A PCR reaction is set up with a template DNA, primers, dNTPs, Taq polymerase, and buffer. After 30 cycles, how many copies of the target DNA are theoretically produced from a single starting molecule?

Accepted Answer

$$2^{30}$$

Question 17

Which of the following statements about PCR primers is correct?

Accepted Answer

Primers are short, single-stranded DNA sequences that flank the target region.

Question 18

In PCR, what is the consequence of using primers with low specificity to the target sequence?

Accepted Answer

Amplification of multiple non-target DNA regions.

Question 19

Which of the following is a critical difference between in vivo DNA replication and in vitro PCR?

Accepted Answer

In vivo replication uses RNA primers and helicase, while PCR uses DNA primers and heat for strand separation.

Question 20

A patient is suspected to carry a mutation in the BRCA1 gene. Which PCR application would be most appropriate for confirming this?

Accepted Answer

Genetic disease mutation detection

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

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