Cellular Division and Replication

Question 1

What is cell populations in adult tissues regulated by?

Answer 1

The relative rates of proliferation, differentiation and death.

Question 2

What is meant by cell proliferation?

Answer 2

• Involves physiological or pathological stimuli
• Controlled by either cell contact or soluble signals

Question 3

How can increased cell proliferation be accomplished?

Answer 3

• By shortening the cell division cycle
• Recruiting inactive cells to divide and proliferate

Question 4

State the three types of cells.

Answer 4

• Labile cells
• Stable cells
• Non-dividing (permanent) cells

Question 5

Describe labile cells.

Answer 5

Constantly dividing, regenerate rapidly e.g. surface epithelium

Question 6

Describe stable cells.

Answer 6

Low level of replicative activity but can rapidly divide in response to stimuli e.g. liver

Question 7

Describe non-dividing (permanent) cells.

Answer 7

Terminally differentiated unable to proliferate e.g. neurons

Question 8

Describe interphase

Answer 8

G1 Phase:
- Period before synthesis of DNA
- Variable in length between cell types
- May be indistinguishable from G0
S phase (synthesis)
- Nuclear DNA is synthesised
- Chromosomes are duplicated
G2 Phase
- After DNA synthesis is complete
-Lasts until cell division (mitosis) phase

Question 9

State and describe the five phases of mitosis.

Answer 9

Prophase: centrioles move to poles

Prometaphase: Microtubules attach to chromosomes

Metaphase: Chromosomes align, nuclei disappears

Anaphase: Chromosomes divide and move to poles

Telophase: Nuclear membrane reappears and cytokinesis occurs

Question 10

Which protein regulates the cell cycle?

Answer 10

Cyclin CDK

Question 11

Describe the action of cyclin-CDK.

Answer 11

1. Cyclin binding changes Cdk exposing its active site.
2. A protein substrate and ATP bind to Cdk - the protein substrate is phosphorylated
3. The phosphorylated protein regulates the cell cycle - each Cdk has specific protein targets.