2. Cell cycle and its regulation

Question 1

Recall the stages of interphase in eukaryotes

Answer 1

G0 = cell cycle machinary dismantled
G1 = decision point
S = synthesis
G2 = decision point

Question 2

Recall the structure and function of centrioles

Answer 2

Contain centrioles: referred to as mother and daughter centrioles
Function: Regulate microtubules (are themselves ma)de of microtubules

Question 3

Summarise the function of prophase

Answer 3

Condensation of chromatin to minimise DNA damage in mitosis; histone wrapping; spindle formation

Question 4

What is the role of the centromere?

Answer 4

Acts as a “belt” in prophase to constrict chromosomes

Question 5

What is a kinetochore?

Answer 5

Develops at point of centromere belt: = key regulator of cell cycle processes around chromosomes

Question 6

How does the kinetochore sense whether it is attached to microtubules?

Answer 6

CENP-E

Question 7

Summarise the process of spindle formation

Answer 7

1. Radial microtubule arrays (asters) form around each centrosome
2. Meet between mother and daughter centrosomes: where they meet they are called “polar microtubules”
3. Direct chromosome migration

Question 8

Summarise the process of cytokinesis

Answer 8

1. Assembly of contractile ring of actin and myosin which squeezes cell to divide it into 2 daughter cells
2. Ring formed at “midbody”
3. Cells cleaved at “cleavage furrow”

Question 9

When is the “spindle assembly” checkpoint?

Answer 9

Between metaphase and anaphase

Question 10

How does the cell signal passage of the spindle-assemble checkpoint

Answer 10

Whilst kinetochore is unattached, singal proteins are emitted
Once attached, these are no longer produced

Question 11

Recall the role of BUB protein kinases in cell-cycle progression

Answer 11

Dissociate from the kinetochore when chromatids are attached to spindle to allow progression to anaphase

Question 12

Give 3 examples of mis-attachment of spindle to kinetochores

Answer 12

Syntelic (both Ks, same centrosome)
Merotelic (more than one microtubule array: one K)
Monotelic (only 1 K is attached)

Question 13

Where i the spindle-assembly checkpoint can an anti-cancer drug be directed?

Answer 13

Can use inhibitor of spindle-assembly checkpoint so that cell thinks kinetochore is attached and precedes to anaphase when it is not yet ready

Question 14

Give an example of how a tumour may bypass a cell-cycle checkpoint

Answer 14

May block ability to re-enter G0 after G1, thus forcing cell straight into mitosis