Question 1

Which experimental result provided evidence that cytoplasmic molecules regulate the progression of the cell cycle?

Accepted Answer

Fusing a G1-phase cell with an S-phase cell caused the G1 nucleus to begin DNA replication.

Question 2

What is the primary function of the cell cycle control system?

Accepted Answer

To ensure that each phase of the cell cycle is completed in the correct sequence and only under appropriate conditions.

Question 3

A liver cell is typically in the G0 phase. What could stimulate it to re-enter the cell cycle?

Accepted Answer

Exposure to external growth factors during tissue repair.

Question 4

Which of the following best describes the role of cyclins in the cell cycle?

Accepted Answer

Cyclins regulate the activity of cyclin-dependent kinases (Cdks) by binding to them.

Question 5

What would most likely happen if a cell does NOT receive a go-ahead signal at the G1 checkpoint?

Accepted Answer

The cell will exit the cycle and enter the G0 phase.

Question 6

Which checkpoint ensures that all chromosomes are properly attached to spindle fibers before anaphase begins?

Accepted Answer

M checkpoint

Question 7

What is the direct molecular action of maturation-promoting factor (MPF) during mitosis initiation?

Accepted Answer

MPF phosphorylates proteins of the nuclear lamina, leading to nuclear envelope breakdown.

Question 8

Which of the following statements about cyclin-dependent kinases (Cdks) is TRUE?

Accepted Answer

Cdks are only active when bound to a cyclin.

Question 9

A nerve cell in an adult human is considered to be in which phase of the cell cycle?

Accepted Answer

G0 phase

Question 10

If a mutation caused a cell to ignore the G1 checkpoint, what is a likely consequence?

Accepted Answer

The cell may divide uncontrollably, potentially leading to cancer.

Question 11

Which of the following best explains why cancer cells can divide uncontrollably?

Accepted Answer

They escape the usual controls on the cell cycle, such as checkpoint regulation.

Question 12

Which of the following is NOT a part of interphase?

Accepted Answer

M phase

Question 13

What is the correct order of the phases in the eukaryotic cell cycle?

Accepted Answer

$$G_1$$ \rightarrow S \rightarrow $$G_2$$ \rightarrow M$$

Question 14

Which of the following events is directly triggered by the activation of MPF at the G2 checkpoint?

Accepted Answer

Initiation of mitosis (M phase)

Question 15

What is the main reason most human cells are found in the G0 phase under normal conditions?

Accepted Answer

They are not actively dividing and are performing specialized functions.

Question 16

Which of the following best describes the restriction point in the cell cycle?

Accepted Answer

A critical checkpoint in G1 that determines if the cell will proceed to divide.

Question 17

What is the fate of a cell that does not receive a go-ahead signal at the restriction point?

Accepted Answer

It enters a non-dividing state called G0.

Question 18

Which of the following is a direct result of MPF activity peaking during the cell cycle?

Accepted Answer

Breakdown of the nuclear envelope and initiation of mitosis.

Question 19

Which of the following is a plausible consequence if a cell's cyclin is not degraded after mitosis?

Accepted Answer

The cell may re-enter mitosis prematurely, leading to abnormal cell division.

Question 20

Which of the following best explains why the cell cycle does not progress randomly?

Accepted Answer

It is regulated by internal signals and checkpoints that ensure proper sequence and timing.

Cell Cycle Pt 2

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