Question 1

During which phase of the cell cycle does DNA replication occur, and what is the ploidy of the cell immediately after this phase?

Accepted Answer

S phase; diploid with replicated chromosomes

Question 2

A researcher observes a cell with chromosomes aligned at the center of the cell, spindle fibers attached to kinetochores, and no visible nuclear envelope. Which stage of mitosis is this cell in?

Accepted Answer

Metaphase

Question 3

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

Accepted Answer

They phosphorylate target proteins to drive the cell cycle forward when bound to cyclins.

Question 4

A cell is observed to have a cleavage furrow forming. Which of the following proteins are directly involved in this process in animal cells?

Accepted Answer

Actin and myosin

Question 5

If a diploid cell (2n = 6) undergoes mitosis and a non-disjunction event occurs during anaphase, what is a possible chromosome number in one of the resulting daughter cells?

Accepted Answer

$$2n - 1 = 5$$

Question 6

Which checkpoint ensures that all chromosomes are properly attached to the spindle before anaphase begins, and what is the main protein complex involved in this process?

Accepted Answer

M-phase checkpoint; anaphase-promoting complex (APC)

Question 7

Which of the following best explains the difference between a proto-oncogene and a tumor suppressor gene?

Accepted Answer

Proto-oncogenes are dominant when mutated, while tumor suppressor genes are recessive when mutated.

Question 8

A scientist is testing a new drug that is hypothesized to decrease the mitotic rate in cultured cells. Which statistical test should be used to determine if the observed difference in mitotic rate is significant, and what is the purpose of this test?

Accepted Answer

Chi-square test; to compare observed and expected frequencies

Question 9

Which of the following events is directly triggered by the phosphorylation of nuclear lamins by cyclin-2/CDK-2 (MPF) after the G2 checkpoint?

Accepted Answer

Breakdown of the nuclear envelope

Question 10

A mutation in the p53 gene is found in a patient's tumor cells. What is the most likely consequence of this mutation?

Accepted Answer

Cells fail to arrest at the G1 checkpoint in response to DNA damage

Question 11

Which of the following best describes the function of telomerase in cancer cells?

Accepted Answer

It maintains telomere length, allowing unlimited cell divisions.

Question 12

Which of the following is a correct null hypothesis for an experiment testing whether a new chemical affects the rate of mitosis in onion root tip cells?

Accepted Answer

The new chemical will have no effect on the rate of mitosis.

Question 13

Which of the following best explains why at least three mutations are typically required to transform a normal cell into a cancerous cell?

Accepted Answer

Multiple mutations are needed to inactivate tumor suppressor genes and activate proto-oncogenes, overcoming normal regulatory mechanisms.

Question 14

Which of the following best describes the role of the kinetochore during mitosis?

Accepted Answer

It is the region where spindle fibers attach to chromosomes to facilitate their movement.

Question 15

A cell is observed to have condensed chromosomes, a reformed nuclear envelope, and the beginning of cytokinesis. Which stage is this cell most likely in?

Accepted Answer

Telophase

Question 16

Which of the following is a key difference between cytokinesis in plant and animal cells?

Accepted Answer

Plant cells form a cell plate, while animal cells form a cleavage furrow.

Question 17

Which of the following best describes the function of separase during mitosis?

Accepted Answer

It cleaves cohesin proteins to allow sister chromatids to separate during anaphase.

Question 18

A cell is arrested at the G1 checkpoint. Which of the following is most likely being checked at this point?

Accepted Answer

DNA damage and sufficient resources for DNA replication

Question 19

Which of the following best describes the role of Ras in the signal transduction pathway controlling the G1 checkpoint?

Accepted Answer

Ras is a GTPase that transmits signals from receptor tyrosine kinases (RTKs) to promote cell cycle progression.

Regulation of the Cell Cycle, Mitosis, and Cancer: Study Guide

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