Question 1

Which enzyme is responsible for unwinding the DNA double helix during replication, and what is the consequence if this enzyme is inhibited?

Accepted Answer

Helicase; replication cannot proceed as the strands remain paired

Question 2

During DNA replication, which strand is synthesized continuously and in which direction does DNA polymerase add nucleotides?

Accepted Answer

Leading strand; 5' to 3' direction

Question 3

What is the function of single-stranded DNA binding proteins (SSBs) during DNA replication?

Accepted Answer

They prevent the reannealing of separated DNA strands

Question 4

Which enzyme is responsible for joining Okazaki fragments on the lagging strand?

Accepted Answer

DNA ligase

Question 5

In eukaryotic DNA replication, what is the role of telomerase?

Accepted Answer

It extends the ends of linear chromosomes to prevent loss of genetic information

Question 6

Which of the following correctly describes the semiconservative nature of DNA replication?

Accepted Answer

Each new DNA molecule consists of one old strand and one new strand

Question 7

What is the main function of DNA polymerase III in prokaryotic DNA replication?

Accepted Answer

Synthesizes new DNA by adding nucleotides to the 3' end

Question 8

Which of the following is NOT a reagent required for a typical PCR reaction?

Accepted Answer

Single-stranded DNA binding proteins

Question 9

During the elongation step of PCR, what is the optimal temperature for DNA polymerase activity?

Accepted Answer

$$72^\circ 	ext{C}$$

Question 10

Which base pairing follows Chargaff's rule in DNA?

Accepted Answer

A pairs with T, G pairs with C

Question 11

What is the chemical reaction catalyzed by DNA polymerase during nucleotide addition?

Accepted Answer

Nucleophilic attack of the 3'-OH group on the innermost phosphorus atom of a dNTP, forming a phosphodiester bond and releasing pyrophosphate ($$PP_i)$$

Question 12

Which enzyme removes RNA primers during DNA replication in prokaryotes?

Accepted Answer

DNA polymerase I

Question 13

A mutation in the gene encoding topoisomerase would most likely result in which of the following during DNA replication?

Accepted Answer

Excessive supercoiling and torsional strain

Question 14

Which step in PCR involves the separation of double-stranded DNA into single strands?

Accepted Answer

Denaturation

Question 15

Why is a thermostable DNA polymerase, such as Taq polymerase, used in PCR?

Accepted Answer

It remains active at high temperatures required for denaturation and extension

Question 16

Which of the following best describes the function of the sliding clamp in DNA replication?

Accepted Answer

It holds DNA polymerase in place during DNA synthesis

Question 17

If a DNA polymerase incorporates a mismatched base, what mechanism ensures the error is corrected?

Accepted Answer

3'-5' exonuclease proofreading activity

Question 18

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

Accepted Answer

Amplifying DNA from a crime scene for forensic analysis

Question 19

During DNA replication, why is the lagging strand synthesized in fragments?

Accepted Answer

Because DNA polymerase can only synthesize in the 5' to 3' direction, and the lagging strand template is oriented 3' to 5'

Question 20

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand during DNA replication

DNA Replication and Polymerase Chain Reaction (PCR): Mechanisms, Enzymes, and Applications

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