Question 1

Which phase of the cell cycle is primarily responsible for the duplication of chromosomes, and what is the main event that occurs during this phase?

Accepted Answer

S phase; DNA is synthesized and chromosomes are duplicated

Question 2

During mitosis, what is the function of the mitotic spindle, and which cellular structure initiates its assembly in animal cells?

Accepted Answer

The mitotic spindle controls chromosome movement; assembly begins at the centrosome

Question 3

A cell is observed to have chromosomes lined up at the metaphase plate. Which stage of mitosis is this, and what is the significance of this arrangement?

Accepted Answer

Metaphase; ensures each daughter cell receives an identical set of chromosomes

Question 4

Which enzyme is responsible for cleaving cohesins during anaphase, and what is the result of this action?

Accepted Answer

Separase; sister chromatids separate and move to opposite poles

Question 5

In animal cells, cytokinesis is accomplished by the formation of a cleavage furrow. What cellular components are involved in this process?

Accepted Answer

Contractile ring of microfilaments (actin)

Question 6

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

Accepted Answer

G1 checkpoint; cell enters a nondividing state called G0

Question 7

Cancer cells often lose the ability to respond to density-dependent inhibition and anchorage dependence. What is the consequence of this loss?

Accepted Answer

Cancer cells divide uncontrollably, forming tumors

Question 8

A researcher observes a cell with two sets of chromosomes in its nucleus. What type of cell is this most likely to be, and what is the significance of this chromosome number?

Accepted Answer

Somatic cell; it is diploid

Question 9

Binary fission is a type of cell division used by prokaryotes. Which of the following best describes the process?

Accepted Answer

Chromosome replicates, and the plasma membrane pinches inward to divide the cell

Question 10

Cyclin-dependent kinases (Cdks) are crucial for cell cycle regulation. What must occur for a Cdk to be active?

Accepted Answer

Cdk must be attached to a cyclin

Question 11

A cell is exposed to platelet-derived growth factor (PDGF). What is the expected response, and which cell type is most likely to be affected?

Accepted Answer

Cell will begin dividing; fibroblasts are affected

Question 12

During which stage of mitosis do the nuclear envelope fragments, and spindle microtubules attach to kinetochores?

Accepted Answer

Prometaphase

Question 13

If a cell fails to properly attach all chromosomes to the spindle at the metaphase plate, what is the likely outcome?

Accepted Answer

The cell will not begin anaphase, preventing chromosome missegregation

Question 14

Which of the following best describes the difference between mitosis and meiosis in terms of genetic outcome?

Accepted Answer

Mitosis produces genetically identical daughter cells; meiosis produces nonidentical daughter cells with half the chromosome number

Question 15

A cell is treated with a drug that inhibits microtubule depolymerization. What effect would this have on mitosis?

Accepted Answer

Sister chromatids would not separate during anaphase

Question 16

A patient is diagnosed with a malignant tumor. Which characteristic distinguishes this tumor from a benign tumor?

Accepted Answer

Malignant tumors invade surrounding tissues and can undergo metastasis

Question 17

Which formula represents the number of chromosomes in a diploid cell after DNA replication but before cell division?

Accepted Answer

$$2n$$ chromosomes, each consisting of two sister chromatids$

Question 18

A cell cycle control system is disrupted, causing cells to skip the G2 checkpoint. What is a potential consequence?

Accepted Answer

Cells may enter mitosis with damaged or unreplicated DNA

Question 19

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

Accepted Answer

$$	ext{MPF activity} = 	ext{Cyclin concentration} 	imes 	ext{Cdk activity}$$

Question 20

A scientist observes a cell plate forming during cytokinesis. Which type of cell is being observed, and what is the significance of the cell plate?

Accepted Answer

Plant cell; cell plate becomes the new cell wall separating daughter cells

The Cell Cycle: Mechanisms and Regulation

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