5c + 5d: Control of the Cell Cycle

Question 1

Why are checkpoints important

Answer 1

To regulate the progression through the cell cycle

Question 2

What are checkpoints

Answer 2

Mechanisms within the cell that assess the condition of the cell during the cell cycle and halt the progression to the next phase until certain requirements are met.

Question 3

What are the cell cycle checkpoints

Answer 3

G1, G2, M

Question 4

What are cyclin proteins

Answer 4

Cycling proteins accumulate during the cell growth are involved in regulating the cell cycle

Question 5

What do cyclins do

Answer 5

Cyclins combine with and activate cyclin- dependant kinases (CDKs)

Active cyclin- CDK complexes phosphorylate proteins that regulate progression through the cycle

if sufficient phosphorylation is reached, progression occurs

Question 6

What is the G1 checkpoint

Answer 6

retinoblastoma (Rb) protein acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication.

G1 cyclin-CDK phosphorylase’s the Rb protein. The phosphorylation inhibits Rb. This allows for the transcription of genes that code for proteins needed for DNA replication. Cells can progress from G1 to S.

Question 7

What is the G2 checkpoint

Answer 7

Assesses the success of DNA replication and any damage to DNA is assessed.

Question 8

What does DNA damage trigger

Answer 8

The activation of several proteins including p53

Question 9

What can p53 do

Answer 9

• stimulate DNA repair
• arrest the cell cycle
• cause cell death (initiate apoptosis)

Question 10

What is the metaphase checkpoint

Answer 10

Controls the progression from metaphase to anaphase.

Progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules.

Question 11

The uncontrolled cell reduction can result in….

Answer 11

A degenerative disease (eg Alzheimer’s)

Question 12

an uncontrolled increase in the rate of the cell cycle may result in..

Answer 12

Tumour formation.

Question 13

What is proto-oncogene

Answer 13

Is a normal gene, usually involved in the control of cell growth and division, which can mutate to form a tumour promoting oncogene.

Question 14

What is apoptosis

Answer 14

The destruction of cell. Programmed cell death.

Question 15

What is apoptosis triggered by

Answer 15

Cell death signals that can be external or internal.

Question 16

External death signals example

Answer 16

Production of death signal molecules from lymphocytes.

Question 17

How do eternal cell death signals work

Answer 17

External death signal molecules bind to a surface receptor protein and trigger a protein cascade within the cytoplasm.

Question 18

Internal cell death signal example

Answer 18

Eg DNA damage causes activation of p53 tumour suppressor proteins

Question 19

Both types of death signal results in the activation of…

Answer 19

Caspases

Question 20

What are caspases

Answer 20

Types of protease enzyme which cause the destruction of the cell

Question 21

Other conditions which initiate apoptosis

Answer 21

absence of growth factors

Question 22

Importance of apoptosis

Answer 22

Apoptosis is essential during development of an organism to remove cells no longer required as development progresses or during metamorphosis.