$$\text{DNA synthesis occurs in the 5' \rightarrow 3' direction}$$

Question 1

Which of the following best explains why eukaryotic chromosomes require multiple origins of replication?

Accepted Answer

Eukaryotic chromosomes contain much more DNA than prokaryotic chromosomes, so multiple origins allow for faster and more efficient replication.

Question 2

During which phase of the cell cycle does the origin recognition complex (ORC) tag the origins of replication in eukaryotic cells?

Accepted Answer

G1 phase

Question 3

What is the primary challenge associated with DNA replication at telomeres in eukaryotic cells?

Accepted Answer

The removal of the RNA primer leaves a gap at the 3’ end of the lagging strand, leading to progressive shortening of the chromosome.

Question 4

Which enzyme is responsible for adding extra repeats onto the G-rich strand’s 3’ end at telomeres?

Accepted Answer

Telomerase

Question 5

In eukaryotic DNA replication, what must occur before DNA polymerases can synthesize new strands?

Accepted Answer

DNA binding proteins (such as histones) must be removed or modified.

Question 6

Which of the following best describes the function of the pre-replication complex (pre-RC) in eukaryotic cells?

Accepted Answer

It assembles at origins of replication and enables the initiation of DNA replication.

Question 7

Which sequence is most commonly found in human telomeres?

Accepted Answer

5’- …(TTAGGG)n …-3’

Question 8

What is the role of the RNA component of telomerase?

Accepted Answer

It serves as a template for adding telomeric repeats to the G-rich strand.

Question 9

Which of the following equations correctly represents the directionality of DNA synthesis?

Accepted Answer

$$	ext{DNA synthesis occurs in the 5' ightarrow 3' direction}$$

Question 10

A mutation prevents the dispersal of pre-RC proteins after DNA replication. What is the most likely consequence?

Accepted Answer

DNA replication will occur multiple times at the same origin within a single cell cycle, leading to over-replication.

Question 11

Which of the following best describes the G-quartet structure formed at telomeres?

Accepted Answer

A closed loop formed by the G-rich strand folding on itself and forming G-G bonds.

Question 12

Which of the following is a key difference between DNA replication in prokaryotes and eukaryotes?

Accepted Answer

Eukaryotes have linear chromosomes with centromeres and telomeres, while prokaryotes have circular chromosomes.

Question 13

If telomerase is inactive in a cell, what is the most likely outcome after several rounds of DNA replication?

Accepted Answer

Chromosomes will progressively shorten, potentially leading to loss of genetic information.

Question 14

Which of the following best describes the process of bi-directional DNA synthesis?

Accepted Answer

DNA synthesis proceeds outward in both directions from each origin, forming two replication forks.

Question 15

Which of the following is a plausible consequence of improper removal or modification of DNA binding proteins during replication?

Accepted Answer

DNA polymerase will be unable to access the DNA template, leading to incomplete replication.

Question 16

A cell is observed to have replication bubbles forming at multiple sites along its chromosomes. What does this indicate about the cell?

Accepted Answer

The cell is eukaryotic and is undergoing DNA replication.

Question 17

Which of the following best describes the role of the centromere in eukaryotic chromosomes?

Accepted Answer

It is the region where sister chromatids are joined and is essential for proper chromosome segregation during mitosis.

Question 18

Which of the following equations represents the number of replication forks formed from $$n$$ origins of replication?

Accepted Answer

$$	ext{Number of forks} = 2n$$

Question 19

A patient’s cells are found to have abnormally short telomeres. Which of the following is the most likely explanation?

Accepted Answer

The patient’s cells have decreased or absent telomerase activity.

DNA Replication in Eukaryotes: Mechanisms, Challenges, and Telomere Maintenance

Guida di studio - Domande di pratica