Cell Cycle

Question 1

What are the 4 phases of the cell cycle?

Answer 1

G1, S, G2, M

Question 2

Define the cell cycle

Answer 2

An orderly sequence of events that allows a cell to duplicate its contents and divide in two

Question 3

Name the 4 essential steps to the cell cycle

Answer 3

Duplicate DNA
Segregate DNA
Maintain size by duplicating other organelles/macromolecules
Coordinate cell growth with cell division

Question 4

What occurs in S phase of the cell cycle?

Answer 4

DNA replication

Question 5

What occurs in the gap phases of the cell cycle?

Answer 5

Cell growth by doubling protein mass/organelles
Get ready for next phase
Monitor environment

Question 6

Why would a cell enter transient G0 phase?

Answer 6

Differentiation

Quiescence

Question 7

Why would a cell enter permanent G0 phase?

Answer 7

Terminal differentiation

Senescence (something wrong)

Question 8

Name the 5 phases of mitosis

Answer 8

Prophase
Prometaphase
Metaphase
Anaphase
Telophase

Question 9

Outline prophase

Answer 9

Chromosomes condense, sister chromatids held together by cohesin
Centrosomes move to opposite poles
Spindles assemble
Kinetochore recognition, binding to centromere
Nuclear envelope breaks down

Question 10

Outline prometaphase

Answer 10

Nuclear envelope disintegration
Chromosomes attach to kinetochores (microtubules)
Tension exerted on chromatids

Question 11

Outline metaphase

Answer 11

Chromosomes align on spindle equator

Kinetochore microtubules attach chromatids to opposite poles of spindle

Question 12

Outline anaphase

Answer 12

Sister chromatids separate
Chromatids move to opposite poles
Poles move further apart

Question 13

Outline telophase

Answer 13

Nuclear envelope reforms
Chromatids de-condense
Cytokinesis initiation
End of mitosis

Question 14

What is the purpose of the cell cycle control system?

Answer 14

Events in set sequence
Each event is completed before the next starts
Are conditions suitable for division?

Question 15

What is the cell cycle controlled by?

Answer 15

Cyclin-Cdk complexes

Question 16

What does Cdk stand for?

Answer 16

Cyclin-dependent kinase

Question 17

What are the 4 major cyclin families, what Cdk-complexes do they operate with, and where in the cell cycle do they operate?

Answer 17

D - G1 (Cdk4 and 6)
E - S (Cdk2)
A - S (Cdk2) and G2 (Cdk1)
B - M (Cdk1)

Question 18

What are Cdks?

Answer 18

Serine-threonine protein kinases

Question 19

Define ‘kinase’

Answer 19

Enzyme that catalyses the transfer of phosphate groups (phosphorylation)

Question 20

Define ‘phosphatase’

Answer 20

Enzyme that catalyses the removal of phosphate group

Question 21

G1 cyclin (cyclin D) produced in response to…

Answer 21

External signals

Question 22

G1/S cyclin (cyclin E) triggers…

Answer 22

Start/entry into cell cycle

Question 23

S phase cyclin (cyclin A) triggers…

Answer 23

DNA replication

Question 24

M phase cyclin (cyclin B) triggers…

Answer 24

Spindle assembly and attachment of microtubules to chromosomes

Question 25

What is CAK?

Answer 25

Cdk-activating kinase

Phosphorylates cyclin-Cdk

Question 26

What is Wee1?

Answer 26

An inhibitory kinase - phosphorylates cyclin-Cdk (for the second time) hence inactivating it

Question 27

What is Cdc25?

Answer 27

Activating phosphatase - removes a phosphate group from cyclin-Cdk to activate it (after CAK and Wee1 activity)