$$\text{Chromosome number} = 46$$, $$\text{Chromatid number} = 92$$

Question 1

Which phase of the cell cycle is responsible for the replication of DNA, and what is the consequence if this phase is skipped?

Accepted Answer

S phase; the cell will not have duplicated chromosomes for division

Question 2

During which mitotic subphase do chromosomes align at the center of the cell, and what structure is responsible for their alignment?

Accepted Answer

Metaphase; mitotic spindle and metaphase plate

Question 3

What is the role of the protein p53 at the G$$_1$$ checkpoint, and what can result from its malfunction?

Accepted Answer

It pauses the cell cycle or initiates apoptosis if DNA is damaged; malfunction can lead to uncontrolled cell division and cancer

Question 4

Which equation best represents the relationship between the number of chromosomes and chromatids in a human cell after S phase but before mitosis?

Accepted Answer

$$	ext{Chromosome number} = 46$$, $$	ext{Chromatid number} = 92$$

Question 5

Which of the following statements correctly describes cytokinesis in plant cells?

Accepted Answer

Vesicles from the Golgi apparatus fuse to form a cell plate

Question 6

What is the function of cyclin-dependent kinases (Cdks) in the cell cycle, and how are they regulated?

Accepted Answer

They attach phosphate groups to proteins to activate them; regulated by cyclin concentration

Question 7

A cell is observed to have condensed chromosomes, a broken nuclear envelope, and microtubules attaching to kinetochores. Which phase is this cell in?

Accepted Answer

Prometaphase

Question 8

Which checkpoint ensures that all chromosomes are properly attached to the spindle apparatus before sister chromatids separate?

Accepted Answer

M-phase checkpoint (between metaphase and anaphase)

Question 9

What is the primary difference between mitosis and meiosis in terms of genetic outcome?

Accepted Answer

Mitosis produces genetically identical cells; meiosis produces genetically different cells

Question 10

If a cell fails to pass the G$$_2$$ checkpoint due to incomplete DNA replication, what is the most likely consequence?

Accepted Answer

MPF will not be activated and the cell will remain in G$$_2$$ phase

Question 11

Which process is most similar to eukaryotic M phase in bacteria, and what is its main difference?

Accepted Answer

Binary fission; bacteria do not form a mitotic spindle

Question 12

What is the role of ubiquitin in the regulation of the cell cycle?

Accepted Answer

It marks cyclin for destruction, turning off MPF

Question 13

Which of the following best describes the function of kinases and phosphatases in cell cycle regulation?

Accepted Answer

Kinases add phosphate groups to proteins, turning them on; phosphatases remove phosphate groups, turning them off

Question 14

A mutation causes a cell to skip the M-phase checkpoint. What is a possible outcome?

Accepted Answer

Chromosomes may not be properly separated, leading to aneuploidy

Question 15

Which of the following is true about the concentration of cyclin and Cdk during the cell cycle?

Accepted Answer

Cyclin concentration cycles; Cdk concentration remains constant

Question 16

During anaphase, which two forces are responsible for the separation of sister chromatids?

Accepted Answer

Kinetochore microtubules shrink and motor proteins of polar microtubules push the poles apart

Question 17

Which of the following events marks the completion of mitosis?

Accepted Answer

Formation of two independent nuclei

Question 18

A researcher observes a cell with a newly formed nuclear envelope and decondensing chromosomes. Which phase is this cell most likely in?

Accepted Answer

Telophase

Question 19

Which of the following is a real-world consequence of a defective p53 gene in human cells?

Accepted Answer

Cells divide uncontrollably, increasing the risk of cancer

Chapter 12: The Cell Cycle – Structure, Phases, and Regulation

Study Guide - Practice Questions