Q: Which of the following equations correctly represents the semi-conservative model of DNA replication?

$$\text{Parent DNA} \rightarrow \text{1 Parent Strand} + \text{1 New Strand}$$

Question 1

Which of the following best describes the role of the G1 checkpoint in the eukaryotic cell cycle?

Accepted Answer

It verifies nutrient availability, growth factors, and DNA damage before allowing entry into S phase.

Question 2

In E. coli, why can cell division occur faster than the time required to replicate the entire genome under ideal conditions?

Accepted Answer

Because multiple rounds of replication can overlap, with initiation for division 2 occurring before division 1 is complete.

Question 3

Which gene product is directly responsible for inhibiting E2F transcription factors and thereby controlling the G1/S transition in the cell cycle?

Accepted Answer

Rb (Retinoblastoma protein)

Question 4

A temperature-sensitive mutant allele in a cell division gene results in normal phenotype at 30°C but cell division failure at 42°C. What is the most likely molecular basis for this phenotype?

Accepted Answer

The protein encoded by the mutant allele misfolds and loses function at high temperature.

Question 5

Which of the following is a consequence of uncoupling DNA replication from the cell cycle, resulting in replication occurring more times than cell division?

Accepted Answer

Formation of polyploid cells

Question 6

What is the function of Dam methylation at GATC sites in E. coli DNA replication?

Accepted Answer

It is required for DnaA binding and initiation of replication at the origin.

Question 7

Which of the following best explains why eukaryotic chromosomes have tens of thousands of origins of replication?

Accepted Answer

To ensure the much larger genome is replicated efficiently within the time constraints of the cell cycle.

Question 8

Which molecular switch is commonly mutated in cancer to promote uncontrolled cell proliferation?

Accepted Answer

Ras-GTP

Question 9

A cell with a loss-of-function mutation in both alleles of the Rb gene is most likely to:

Accepted Answer

Undergo uncontrolled cell division, increasing risk of tumorigenesis.

Question 10

Which of the following equations correctly represents the semi-conservative model of DNA replication?

Accepted Answer

$$	ext{Parent DNA} ightarrow 	ext{1 Parent Strand} + 	ext{1 New Strand}$$

Question 11

Which checkpoint gene is stabilized in response to DNA damage and can induce cell cycle arrest or apoptosis?

Accepted Answer

p53

Question 12

In bacterial cell division, which protein is involved in septum formation and is analogous to actin in eukaryotes?

Accepted Answer

MreB

Question 13

Which of the following is an intrinsic limiting factor for the cell cycle in E. coli?

Accepted Answer

The time required to replicate the entire genome

Question 14

Which process is regulated by the ratio of MinE/MinCD proteins in bacterial cell division?

Accepted Answer

Septum placement and Z-ring assembly

Question 15

A cell is found to have a hypermorphic mutation in a growth factor receptor, resulting in constitutive activation. What is the most likely outcome?

Accepted Answer

Uncontrolled cell proliferation, potentially leading to cancer

Question 16

Which of the following best describes the function of cyclin-dependent kinases (CDKs) in the cell cycle?

Accepted Answer

They require binding to cyclins and phosphorylation for activation, controlling progression through cell cycle phases.

Question 17

Which of the following is a plausible consequence of a loss-of-function mutation in a gene required for septum formation in bacteria?

Accepted Answer

Formation of multinucleate filamentous cells due to failure in cell division

Question 18

Which of the following is true regarding the licensing of replication origins in eukaryotes?

Accepted Answer

Licensing factors are only active when replication is needed and are inactivated after origin firing.

Question 19

Which of the following best explains why most cells in an adult multicellular organism are not capable of dividing?

Accepted Answer

They are terminally differentiated and regulated by epigenetic mechanisms.

Cell Cycle, DNA Replication, and Regulation in Genetics

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