Question 1

Which phase of the cell cycle is responsible for the duplication of chromosomes, and what is the consequence of this duplication for the daughter cells?

Accepted Answer

S phase; daughter cells are genetically identical to the parent cell

Question 2

During which stage of mitosis do the sister chromatids separate and move toward opposite poles of the cell, and what enzyme is responsible for cleaving the cohesins?

Accepted Answer

Anaphase; separase

Question 3

What is the role of cyclin-dependent kinases (Cdks) in the cell cycle, and how is their activity regulated?

Accepted Answer

Cdks phosphorylate target proteins to regulate cell cycle progression; their activity depends on binding to cyclins

Question 4

A researcher observes that cultured animal cells stop dividing when they become crowded and are not attached to a surface. Which two phenomena are being demonstrated?

Accepted Answer

Density-dependent inhibition and anchorage dependence

Question 5

Which checkpoint in the cell cycle is considered the most important for many cells, and what happens if a cell does not receive a go-ahead signal at this checkpoint?

Accepted Answer

G$_1$ checkpoint; the cell enters a nondividing state called G$_0$

Question 6

How do cancer cells differ from normal cells in their response to growth factors and cell cycle controls?

Accepted Answer

Cancer cells do not stop dividing when growth factors are depleted and may have abnormal cell cycle control systems

Question 7

In binary fission, which is the primary method of cell division in prokaryotes, what is the sequence of events leading to the formation of two daughter cells?

Accepted Answer

Chromosome replicates, daughter chromosomes move apart, plasma membrane pinches inward, cell divides

Question 8

A cell with 2n chromosomes undergoes mitosis. What is the chromosome number in each daughter cell after cytokinesis?

Accepted Answer

$2n$

Question 9

Which structure is responsible for organizing the mitotic spindle in animal cells, and what happens to it during cell division?

Accepted Answer

Centrosome; it replicates during interphase and migrates to opposite ends of the cell

Question 10

A mutation causes a cell to produce a cyclin that cannot be degraded. What is the most likely consequence for the cell cycle?

Accepted Answer

The cell will continuously pass the G$_2$ checkpoint and may divide uncontrollably

Question 11

Which of the following best describes the difference between somatic cells and gametes in terms of chromosome number?

Accepted Answer

Somatic cells have two sets of chromosomes, while gametes have one set

Question 12

During cytokinesis in animal cells, what structure forms to separate the two daughter cells, and what is its mechanism?

Accepted Answer

Cleavage furrow; a contractile ring of actin microfilaments pinches the cell in two

Question 13

Which molecular complex triggers a cell’s passage past the G$_2$ checkpoint into M phase, and what are its components?

Accepted Answer

MPF; composed of cyclin and cyclin-dependent kinase (Cdk)

Question 14

A patient’s biopsy reveals a mass of abnormal cells that remain at the original site and do not invade surrounding tissues. What is this mass called?

Accepted Answer

Benign tumor

Question 15

Which of the following is NOT a function of cell division in multicellular organisms?

Accepted Answer

Production of gametes for sexual reproduction

Question 16

If a cell receives a signal to divide but is not attached to a substratum, what is likely to happen?

Accepted Answer

The cell will not divide due to lack of anchorage dependence

Question 17

Which of the following best explains why cancer cells can form tumors?

Accepted Answer

They escape normal cell cycle controls and divide indefinitely

Question 18

A scientist fuses a cell in S phase with a cell in G$_1$ phase. What is the most likely outcome for the G$_1$ nucleus?

Accepted Answer

It will begin DNA synthesis and enter S phase

Question 19

Which of the following statements about chromatin and chromosomes is correct?

Accepted Answer

Chromosomes consist of chromatin, which is DNA and protein

Question 20

A cell is observed to have chromosomes aligned at the metaphase plate. Which stage of mitosis is this, and what is the next event?

Accepted Answer

Metaphase; sister chromatids will separate and move to opposite poles

The Cell Cycle: Structure, Function, and Regulation

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