$$DNA_{G2} = 2 \times DNA_{G1}$$

Question 1

Which phase of the cell cycle is primarily responsible for the duplication of chromosomes?

Accepted Answer

S phase

Question 2

A researcher stains cells and observes that some have twice the DNA content of others. Which phase are these cells most likely in?

Accepted Answer

S phase

Question 3

What is the main function of cyclins in the cell cycle?

Accepted Answer

To activate cyclin-dependent kinases (Cdks)

Question 4

Which checkpoint ensures that all chromosomes are properly attached to the spindle before anaphase begins?

Accepted Answer

Metaphase-to-anaphase transition

Question 5

A mutation in the gene encoding Wee1 kinase would most likely result in which of the following?

Accepted Answer

Premature entry into mitosis

Question 6

Which of the following best describes the role of the Anaphase Promoting Complex/Cyclosome (APC/C) in the cell cycle?

Accepted Answer

It degrades securin to allow sister chromatid separation

Question 7

If a cell is exposed to DNA-damaging agents, which protein is most likely to be activated to halt the cell cycle?

Accepted Answer

p53

Question 8

During which phase does the nuclear envelope break down and chromosomes condense?

Accepted Answer

Prophase

Question 9

Which of the following equations correctly represents the DNA content of a cell in G2 phase compared to G1 phase?

Accepted Answer

$$DNA_{G2} = 2 	imes DNA_{G1}$$

Question 10

A cell is unable to degrade M-cyclin at the end of mitosis. What is the most likely consequence?

Accepted Answer

The cell will be unable to exit mitosis

Question 11

Which protein complex is responsible for holding sister chromatids together after DNA replication?

Accepted Answer

Cohesin

Question 12

What is the effect of p27 binding to a cyclin-Cdk complex?

Accepted Answer

It inactivates the complex

Question 13

Which of the following best explains the positive feedback loop involving M-Cdk during mitosis?

Accepted Answer

M-Cdk activates Cdc25 phosphatase, which activates more M-Cdk

Question 14

A cell is observed to have high levels of S-cyclin and active S-Cdk. Which process is most likely occurring?

Accepted Answer

DNA replication

Question 15

Which of the following events is directly triggered by the activation of APC/C at the metaphase-anaphase transition?

Accepted Answer

Separation of sister chromatids

Question 16

If a cell fails the G1 checkpoint due to unfavorable environmental conditions, what is the most likely outcome?

Accepted Answer

The cell will enter a quiescent state (G0)

Question 17

Which of the following best describes the role of condensin proteins during mitosis?

Accepted Answer

They help condense chromosomes for segregation

Question 18

A cell is treated with a drug that inhibits Cdc25 phosphatase. What is the most likely effect on the cell cycle?

Accepted Answer

The cell will arrest in G2 phase

Question 19

Which equation best represents the relationship between cyclin concentration and Cdk activity?

Accepted Answer

$$Cdk_{activity} \propto [cyclin]$$

Question 20

A patient’s cells are found to have a mutation that prevents the degradation of securin. What is the most likely cellular consequence?

Accepted Answer

Sister chromatids will not separate during anaphase

The Eukaryotic Cell Cycle: Regulation, Control, and Key Molecular Players

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