Control of the Cell Cycle

Question 1

Cell Cycle Control System

Answer 1

Cyclical set of molecules that triggers and coordinates main events in the eukaryotic cell cycle. It makes sure events occur only once, at proper times, and in the correct order.

Question 2

Checkpoint

Answer 2

Point where stop and go-ahead signals monitor process of cell cycle

(Signal trandsuction pathways launches the signals)

Question 3

3 Major Checkpoints

Answer 3

G₁ Checkpoint

G₂ Checkpoint

M Checkpoint

(These checkpoints correspond to the 3 phases in the cell cycle)

Question 4

What does the G₁ Checkpoint check?

Answer 4

1. Cell Size
2. Genetic Material

If the genetic material is NOT damaged. If it is damaged, then the process is delayed and the genetic material is repaired. If there is a stop signal, the cell exits and enters G_0.

Question 5

G₀ Phase

Answer 5

State in which cells leave the cell cycle and do NOT divide

(Most cells in our bodies are in the G₀ phase)

Question 6

What does the G₂ Checkpoint check?

Answer 6

1. Genetic Material Duplication
2. Cell Size
3. Genetic Material Completeness

If damage is detected, chromosomes are repaired

Question 7

What does the M Checkpoint check?

Answer 7

1. Genetic Material Attachment

If all chromosomes are attached to spindle fibers from both poles

Question 8

External physical factors that effect cell division

Answer 8

1. Growth Factors
2. Density-dependent Inhibition
3. Anchorage Dependence

Question 9

Growth Factors

Answer 9

Proteins received in the plasma membrane that stimulate cells to divide

Question 10

Density-dependent Inhibition

Answer 10

Contact with other cells causes an animal cell to stop dividing

Question 11

Anchorage Dependence

Answer 11

Requirement that a cell must be attached to a substratum, such as the inside of a culture flask, in order for the cell to divide

Question 12

Cancer Cells

Answer 12

Cancer cells do not respond to signals that trigger checkpoints in the control system; thus, they grow and divide rapidly. Density-dependent inhibition and anchorage dependence do not effect cancer cells.

(Cancer is a disease of the cell cycle.)

Question 13

CDKs

Cyclin-dependent kinases

Answer 13

Proteins that advance cells past checkpoints and through the cycle.

Kinases that phosphorylate other proteins

Question 14

Cyclin

Answer 14

Activate Cdks and help control progression from one stage of the cell cycle to the next. After the cell passes a checkpoint, the cyclins are destroyed, and specific new cyclins for the next checkpoint emerge.