Question 1

During which phase of the cell cycle does DNA replication occur, and what is the main purpose of this phase?

Accepted Answer

S phase; to duplicate the cell's DNA so each daughter cell receives a complete genome

Question 2

Which structure is responsible for organizing microtubules of the spindle during mitosis, and what is its role?

Accepted Answer

Centrosome; duplicates during interphase and organizes spindle microtubules

Question 3

A researcher observes a cell with chromosomes aligned at the metaphase plate, each attached to spindle fibers at their kinetochores. Which phase is this cell in, and what is the significance of this arrangement?

Accepted Answer

Metaphase; ensures that each daughter cell will receive one copy of each chromosome

Question 4

In animal cells, cytokinesis is accomplished by the formation of a cleavage furrow. Which cytoskeletal element is primarily responsible for this process, and how does it function?

Accepted Answer

Actin microfilaments; by forming a contractile ring that pinches the cell in two

Question 5

Which of the following best describes the difference between cytokinesis in plant and animal cells?

Accepted Answer

Plant cells form a cell plate due to the presence of a cell wall, while animal cells form a cleavage furrow

Question 6

A mutation prevents the formation of kinetochores in a dividing cell. What is the most likely consequence of this mutation during mitosis?

Accepted Answer

Spindle fibers will be unable to attach to chromosomes, preventing proper chromosome segregation

Question 7

Which checkpoint in the cell cycle is known as the 'restriction point' and determines whether a cell will proceed with division?

Accepted Answer

G1 checkpoint

Question 8

Binary fission in bacteria differs from mitosis in eukaryotes in which of the following ways?

Accepted Answer

Bacterial chromosomes are circular and replicate from a single origin, while eukaryotic chromosomes are linear and use multiple origins

Question 9

A cell is observed to have a single, circular DNA molecule attached to the plasma membrane, and division occurs by the membrane pinching inward. Which process is being described?

Accepted Answer

Binary fission in prokaryotes

Question 10

During which phase of mitosis do sister chromatids separate and move toward opposite poles of the cell, and what mechanism drives this movement?

Accepted Answer

Anaphase; motor proteins move chromatids along microtubules, which depolymerize at the kinetochore ends

Question 11

If a cell spends 90% of its cycle in interphase, and the total cell cycle is 24 hours, approximately how long does mitosis (M phase) last?

Accepted Answer

$$24 	imes 0.10 = 2.4$$ hours

Question 12

Which of the following is a key evolutionary insight about mitosis based on the comparison with binary fission?

Accepted Answer

Proteins involved in bacterial binary fission are related to eukaryotic proteins used in mitosis, suggesting evolutionary continuity

Question 13

A scientist observes a cell with two asters at opposite poles, chromosomes aligned at the center, and spindle fibers attached to kinetochores. What would be the next event in the cell cycle?

Accepted Answer

Sister chromatids will separate and move to opposite poles (anaphase)

Question 14

Which of the following best explains why plant cells do not form a cleavage furrow during cytokinesis?

Accepted Answer

The presence of a rigid cell wall requires the formation of a cell plate instead

Question 15

If a mutation caused a cell to skip the G2 phase, which of the following would most likely be affected?

Accepted Answer

Final growth and preparation for mitosis

Question 16

Which of the following events occurs during prometaphase of mitosis?

Accepted Answer

Nuclear envelope fragments and spindle fibers attach to kinetochores

Question 17

A cell is observed to have entered a non-dividing state called G0. Which of the following is true about this cell?

Accepted Answer

It has exited the cell cycle and is not preparing to divide

Question 18

Which of the following best describes the role of the spindle checkpoint during mitosis?

Accepted Answer

It verifies that all chromosomes are properly attached to spindle fibers before anaphase proceeds

Question 19

In binary fission, what is the correct sequence of events for chromosome replication and cell division?

Accepted Answer

Chromosome replication begins, cell elongates, plasma membrane pinches inward, two daughter cells result

Cell Cycle, Mitosis, and Binary Fission: Key Concepts and Mechanisms

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