Question 1

Which of the following best describes the semi-conservative model of DNA replication?

Accepted Answer

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

Question 2

During DNA synthesis, which enzyme is responsible for relieving the tension ahead of the replication fork caused by unwinding of the DNA double helix?

Accepted Answer

Topoisomerase

Question 3

Why is an RNA primer necessary for DNA polymerase to begin synthesis of a new DNA strand?

Accepted Answer

DNA polymerase can only add nucleotides to an existing 3' end.

Question 4

Which of the following equations correctly represents the direction in which new DNA is synthesized?

Accepted Answer

$$5' \rightarrow 3'$$

Question 5

What is the role of single-strand binding proteins (SSBs) during DNA replication?

Accepted Answer

They stabilize separated DNA strands to prevent re-annealing.

Question 6

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

Accepted Answer

Multiple origins allow the large amount of DNA to be replicated quickly.

Question 7

Which enzyme is responsible for synthesizing short RNA primers on the lagging strand during DNA replication?

Accepted Answer

Primase

Question 8

What is the main difference between the synthesis of the leading and lagging strands during DNA replication?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments.

Question 9

Okazaki fragments are associated with which aspect of DNA replication?

Accepted Answer

Discontinuous synthesis of the lagging strand

Question 10

Why does eukaryotic DNA shorten with each round of replication?

Accepted Answer

DNA polymerase cannot complete the 5' end of the new strand after removal of the RNA primer.

Question 11

How do telomeres protect genes at the ends of eukaryotic chromosomes?

Accepted Answer

They consist of non-coding, repetitive DNA sequences that are lost instead of genes during replication.

Question 12

Which enzyme extends telomeres in certain cell types by adding repetitive DNA sequences using an RNA template?

Accepted Answer

Telomerase

Question 13

In humans, telomerase is most active in which type of cells?

Accepted Answer

Rapidly dividing cells such as germline, embryonic, and stem cells

Question 14

Which of the following best explains why reactivation of telomerase is associated with cancer cell immortality?

Accepted Answer

Telomerase prevents telomere shortening, allowing unlimited cell divisions.

Question 15

Which of the following equations represents the reaction catalyzed by DNA polymerase during DNA synthesis?

Accepted Answer

$$	ext{(dNMP)}_n + 	ext{dNTP} ightarrow 	ext{(dNMP)}_{n+1} + PP_i$$

Question 16

A mutation disables the function of primase in a cell. Which immediate effect would you expect during DNA replication?

Accepted Answer

No RNA primers would be made, so DNA polymerase could not initiate DNA synthesis.

Question 17

Which of the following is a direct energy source for the formation of phosphodiester bonds during DNA synthesis?

Accepted Answer

Hydrolysis of the incoming deoxynucleoside triphosphate (dNTP)

Question 18

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

Accepted Answer

DNA ligase

Question 19

A bacterial cell is exposed to a drug that inhibits topoisomerase. What is the most likely consequence during DNA replication?

Accepted Answer

Excessive supercoiling and possible breakage of DNA ahead of the replication fork.

Question 20

Which of the following statements about DNA replication in prokaryotes and eukaryotes is correct?

Accepted Answer

Prokaryotes typically have a single origin of replication, while eukaryotes have hundreds to thousands.

Week 8 - Oct 29

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