Question 1

During which phase of the cell cycle does DNA replication occur, and what is the significance of this event for mitosis?

Accepted Answer

DNA replication occurs during the S phase, allowing each chromosome to consist of two sister chromatids for accurate segregation during mitosis.

Question 2

Which structure is responsible for organizing the mitotic spindle in animal cells, and what is its role during mitosis?

Accepted Answer

The centrosome organizes the spindle microtubules, ensuring proper chromosome movement during mitosis.

Question 3

What is the function of the kinetochore during mitosis?

Accepted Answer

The kinetochore is a protein complex that attaches chromosomes to spindle microtubules, facilitating their movement during anaphase.

Question 4

Which equation best represents the change in chromosome number during mitosis in a human somatic cell?

Accepted Answer

$$2n \rightarrow 2n$$

Question 5

A researcher observes a cell with condensed chromosomes aligned at the center of the cell. Which phase of mitosis is this, and what is the significance of this alignment?

Accepted Answer

Metaphase; this alignment ensures that each daughter cell receives an identical set of chromosomes.

Question 6

How does cytokinesis differ between animal and plant cells?

Accepted Answer

Animal cells form a cleavage furrow, while plant cells form a cell plate.

Question 7

Which checkpoint in the cell cycle ensures that all chromosomes are properly attached to the spindle before proceeding to anaphase?

Accepted Answer

M checkpoint

Question 8

What is the role of cyclin-dependent kinases (Cdks) in the cell cycle?

Accepted Answer

Cdks phosphorylate target proteins only when bound to cyclins, regulating progression through cell cycle checkpoints.

Question 9

A mutation in the p53 tumor suppressor gene can lead to cancer. Which of the following best explains why?

Accepted Answer

p53 normally activates DNA repair and cell cycle arrest; its loss allows cells with damaged DNA to continue dividing.

Question 10

Which of the following is a plausible consequence of a mutation that converts a proto-oncogene to an oncogene?

Accepted Answer

Uncontrolled cell division due to increased activity or expression of growth-promoting proteins.

Question 11

In binary fission, which equation best represents the chromosome number change in bacteria?

Accepted Answer

$$1 \rightarrow 1$$

Question 12

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

Accepted Answer

Cohesins hold sister chromatids together until anaphase, when they are cleaved to allow chromatid separation.

Question 13

A cell is exposed to a chemotherapeutic drug that targets rapidly dividing cells. Which phase of the cell cycle is most likely affected?

Accepted Answer

M phase

Question 14

Which of the following is NOT a function of tumor-suppressor proteins?

Accepted Answer

Stimulating cell division

Question 15

Which of the following best explains why cancer incidence increases with age?

Accepted Answer

Multiple mutations accumulate over time, increasing the likelihood of oncogene activation and tumor-suppressor gene inactivation.

Question 16

A patient inherits a mutant allele of the BRCA1 gene. What is the most likely consequence?

Accepted Answer

Increased predisposition to certain cancers due to impaired DNA repair and cell cycle control.

Question 17

Which of the following best describes the relationship between cyclin concentration and MPF activity?

Accepted Answer

MPF activity peaks when cyclin concentration is highest, triggering entry into the M phase.

Question 18

Which of the following is a real-world example of cell division for tissue renewal?

Accepted Answer

Skin cells dividing to repair a wound after injury.

Question 19

Which of the following best describes the process of chromosome movement during anaphase?

Accepted Answer

Motor proteins at the kinetochores walk the chromosomes along microtubules, which depolymerize at the kinetochore ends.

Question 20

Which of the following is a key difference between mitosis and meiosis?

Accepted Answer

Mitosis produces genetically identical daughter cells, while meiosis produces nonidentical cells with half the chromosome number.

The Cell Cycle and Molecular Biology of Cancer: Study Notes for General Biology

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