Question 1

Which enzyme is primarily responsible for unwinding the DNA double helix during the initial stage of DNA replication?

Accepted Answer

Helicase

Question 2

During DNA replication, what is the main function of primase?

Accepted Answer

To insert an RNA primer marking the starting point for nucleotide addition

Question 3

Which of the following best describes semi-conservative replication?

Accepted Answer

Each new DNA molecule contains one original and one new strand

Question 4

A mutation occurs during DNA replication. Which sequence of enzyme actions is most likely to repair this mutation?

Accepted Answer

READ enzymes recognize mismatch, CUT enzymes remove error, REPLACE enzymes insert correct nucleotide

Question 5

Which strand is synthesized continuously during DNA replication, and in which direction does this synthesis occur?

Accepted Answer

Leading strand; 5' to 3'

Question 6

Okazaki fragments are associated with which aspect of DNA replication?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand

Question 7

If a cell is exposed to a chemical mutagen during S-phase, which of the following is most likely to occur if the mutation is not repaired before mitosis?

Accepted Answer

The mutation may be passed on to both daughter cells

Question 8

Which of the following best explains why multiple replication bubbles form during DNA replication in eukaryotic cells?

Accepted Answer

To speed up the replication process by allowing simultaneous replication at multiple sites

Question 9

A scientist observes that after DNA replication, each daughter DNA molecule consists of one old and one new strand. Which experimental result would best support this observation?

Accepted Answer

Only one strand in each daughter DNA is labeled with a radioactive isotope

Question 10

Which enzyme is responsible for connecting the gaps between Okazaki fragments on the lagging strand?

Accepted Answer

Ligase

Question 11

If the DNA sequence on the template strand is 5'-ATCGGTA-3', what is the sequence of the newly synthesized complementary strand?

Accepted Answer

3'-TAGCCAT-5'

Question 12

Which of the following is NOT a possible cause of DNA mutations as described in the study materials?

Accepted Answer

Normal DNA polymerase activity

Question 13

During which phase of the cell cycle does DNA replication occur?

Accepted Answer

S phase

Question 14

Which of the following best describes the role of single-stranded binding proteins during DNA replication?

Accepted Answer

They prevent the separated DNA strands from re-annealing

Question 15

A patient is exposed to UV radiation, which causes thymine dimers in DNA. Which repair mechanism is most likely to be activated?

Accepted Answer

READ, CUT, and REPLACE enzymes

Question 16

If DNA polymerase makes a mistake and inserts an incorrect nucleotide, what is the immediate consequence if the error is not repaired?

Accepted Answer

A mutation will be present in the daughter DNA

Question 17

Which of the following statements about DNA replication is correct?

Accepted Answer

The lagging strand is synthesized in short fragments

Question 18

A cell completes DNA replication in 7 hours, copying 3 billion base pairs. What is the average rate of nucleotide addition per second?

Accepted Answer

$$\frac{3,000,000,000}{7 	imes 60 	imes 60} \approx 119,048$$ nucleotides/second

Question 19

Which of the following is a potential positive outcome of a DNA mutation?

Accepted Answer

It can contribute to genetic diversity

Question 20

Which of the following sequences correctly represents the order of events during DNA replication?

Accepted Answer

Helicase unwinds DNA, primase adds RNA primer, DNA polymerase adds nucleotides, ligase joins fragments

DNA Replication and Repair: Human Biology Study Notes

Study Guide - Practice Questions

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