Question 1

Which statement best describes the semi-conservative nature of DNA replication?

Accepted Answer

Each daughter DNA molecule contains one parental strand and one newly synthesized strand.

Question 2

During DNA synthesis in prokaryotes, what is the role of the RNA primer?

Accepted Answer

It provides a 3' hydroxyl group for DNA polymerase to begin synthesis.

Question 3

Which enzyme is responsible for unwinding the DNA double helix during replication?

Accepted Answer

DNA helicase

Question 4

In eukaryotic DNA replication, why are multiple origins of replication necessary?

Accepted Answer

Eukaryotic chromosomes are large and linear, so multiple origins allow rapid and complete replication.

Question 5

Which of the following best explains the difference between leading and lagging strand synthesis?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously as Okazaki fragments.

Question 6

What is the function of DNA ligase during DNA replication?

Accepted Answer

It joins Okazaki fragments by sealing nicks in the sugar-phosphate backbone.

Question 7

Which equation correctly represents the removal of two phosphates during nucleotide incorporation in DNA synthesis?

Accepted Answer

$$dNTP \rightarrow dNMP + PP_i$$

Question 8

A mutation causes the loss of an amino group from cytosine, converting it to uracil. What type of mutation is this?

Accepted Answer

Deamination

Question 9

Which repair mechanism is most likely to fix a thymine dimer caused by UV radiation?

Accepted Answer

Excision repair

Question 10

In E. coli, how does the mismatch repair system distinguish the newly synthesized DNA strand from the parental strand?

Accepted Answer

By differences in DNA methylation between the parent and newly synthesized strand.

Question 11

Which of the following best describes the role of telomerase in eukaryotic cells?

Accepted Answer

It adds repetitive DNA sequences to the ends of chromosomes to prevent shortening during replication.

Question 12

A patient is exposed to a chemical mutagen that acts as a base analog. What is the most likely effect on their DNA?

Accepted Answer

The base analog will substitute for a normal base, potentially causing mispairing during replication.

Question 13

Which enzyme has 3' to 5' exonuclease activity for proofreading during DNA replication?

Accepted Answer

DNA polymerase

Question 14

If a mutation occurs during DNA replication and is not corrected by proofreading, which repair system is most likely to correct it after replication?

Accepted Answer

Mismatch repair

Question 15

Which of the following is a consequence of depurination in DNA?

Accepted Answer

Loss of a purine base from the DNA backbone

Question 16

A scientist observes that DNA replication in a cell is proceeding in both directions from a single origin. What is this process called?

Accepted Answer

Bidirectional replication

Question 17

Which of the following best explains why Okazaki fragments are formed during DNA replication?

Accepted Answer

DNA polymerase can only synthesize DNA in the 5' to 3' direction, so the lagging strand is synthesized discontinuously.

Question 18

Which of the following is NOT a function of DNA polymerase during replication?

Accepted Answer

Removing RNA primers

Question 19

A cell is exposed to UV radiation, resulting in the formation of covalent bonds between adjacent thymine bases. What is this type of DNA damage called?

Accepted Answer

Thymine dimer

Question 20

Which of the following steps occurs LAST during the excision repair of DNA?

Accepted Answer

DNA ligase seals the newly synthesized DNA into the backbone.

DNA Replication and Repair: Mechanisms and Regulation

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