Question 1

Which of the following best describes the direction in which DNA polymerase synthesizes a new DNA strand during replication?

Accepted Answer

5' to 3'

Question 2

During DNA replication, which enzyme is responsible for unwinding the double helix by breaking hydrogen bonds between base pairs?

Accepted Answer

DNA helicase

Question 3

What is the role of RNA primase during DNA replication?

Accepted Answer

It synthesizes short RNA primers to provide a 3' OH group for DNA polymerase.

Question 4

Which of the following statements about the structure of DNA is correct?

Accepted Answer

The two strands are antiparallel and held together by hydrogen bonds between complementary bases.

Question 5

Which enzyme is responsible for replacing RNA primers with DNA nucleotides during DNA replication?

Accepted Answer

DNA polymerase

Question 6

What is the function of DNA ligase during DNA replication?

Accepted Answer

It forms the final phosphodiester bond between adjacent DNA fragments.

Question 7

Which of the following base pairs is held together by three hydrogen bonds?

Accepted Answer

Guanine and Cytosine

Question 8

If a mutation occurs during DNA replication and is not corrected by proofreading, what is the most likely consequence?

Accepted Answer

A permanent change in the DNA sequence (mutation)

Question 9

Which of the following best explains why DNA replication is described as 'semi-conservative'?

Accepted Answer

Each new DNA molecule consists of one parental strand and one newly synthesized strand.

Question 10

Which of the following sequences could be a possible RNA primer synthesized during DNA replication if the template DNA sequence is 5'-ATGCCG-3'?

Accepted Answer

5'-CGGCAU-3'

Question 11

Which of the following best describes the chemical reaction that forms the phosphodiester bond between nucleotides in DNA?

Accepted Answer

Dehydration synthesis (condensation reaction)

Question 12

A scientist observes that a DNA molecule has 30% adenine. According to Chargaff's rules, what percentage of thymine should be present?

Accepted Answer

$$30\%$$

Question 13

Which of the following is NOT a property of DNA that is essential for life?

Accepted Answer

DNA can directly catalyze protein synthesis.

Question 14

During DNA replication, what is the immediate consequence if DNA polymerase fails to proofread and correct a mismatched base?

Accepted Answer

A mutation is introduced into the DNA sequence.

Question 15

Which of the following best explains why the lagging strand is synthesized discontinuously?

Accepted Answer

DNA polymerase can only add nucleotides to the 3' end, so it must work in short fragments away from the replication fork.

Question 16

Which of the following is the correct sequence of events during DNA replication?

Accepted Answer

Helicase unwinds DNA, primase synthesizes RNA primer, DNA polymerase extends DNA, ligase seals nicks.

Question 17

Which of the following best describes the backbone of a DNA molecule?

Accepted Answer

Alternating sugar and phosphate groups

Question 18

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

Accepted Answer

Okazaki fragments would not be joined together on the lagging strand.

Question 19

Which of the following is a direct result of the antiparallel structure of DNA?

Accepted Answer

One strand is synthesized continuously and the other discontinuously during replication.

Question 20

Which of the following best explains why mutations are important for evolution?

Accepted Answer

Mutations introduce genetic variation, which is the raw material for evolution.

DNA Replication and Structure: Study Notes for General Biology

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