Week 4 - Cell cycle

Question 1

Prophase

Answer 1

Chromatin condensation
Nucleolus disappears
Centrioles move to poles

Question 2

Pro-metaphase

Answer 2

Nuclear membrane dissolves
Chromosomes attach to microtubules and begin moving

Question 3

Metaphase

Answer 3

Spindle fibres align the chromosomes along the middle of the cell nucleus (metaphase plate)

Question 4

Anaphase

Answer 4

Paired chromosomes separate and move to opposite sides of the cell

Question 5

Telophase

Answer 5

Chromatids arrive at the opposite poles of cell
New membranes form around daughter nuclei
Chromosomes decondense
Spindle fibres disperse

Question 6

How long roughly does the entire cell cycle take

Answer 6

24 hours

Question 7

4 things that happen during G1 phase

Answer 7

Growing in size
Monitoring development
RNA and protein synthesis in preparation for S phase
Growth-factor dependent

Question 8

3 things that happen during G2 phase

Answer 8

Further growth
Cell organelle replication
Preparation for mitosis

Question 9

What happens during S phase

Answer 9

Synthesis of DNA

Question 10

What is another name for G0 phase and give an example of a cell like this

Answer 10

Quiescent e.g erythrocyte

Question 11

What is the role of cyclin-dependent kinases

Answer 11

Regulate the progression through the cell cycle

Question 12

What else can CDKs be dependent on? (I think)

Answer 12

Cyclins
Phosphorylation/dephosphorylation
CKIs

Question 13

Which CDK and cyclin at end of G1

Answer 13

CDK4/6-cyclin D

Question 14

Which CDK and cyclin during S

Answer 14

CDK2-cyclin E

Question 15

Which CDK and cyclin between S and M

Answer 15

CDK2 - cyclin A

Question 16

Which CDK and cyclin at end of G2 and mainly during mitosis

Answer 16

CDK1-cyclin B

Question 17

3 families of CDK inhibitors

Answer 17

p21 CIP

p27 KIP

p16 INK

Question 18

How do CDK inhibitors work

Answer 18

by forming an inactive complex or by acting as a competitive CDK ligand

Question 19

What else is cyclin B/CDK1 known as

Answer 19

Maturation promoting factor

Question 20

Which cyclin level starts to increase during G2

Answer 20

Cyclin B

Question 21

What does maturation promoting factor do

Answer 21

It breaks down the nuclear envelope (breaks down the lamina)

Condenses chromosomes

Forms spindles (microtubule-associated proteins)

Question 22

Where are the 4 checkpoints on the cell cycle and what does each do

Answer 22

Restriction point (G1) - checks for cell size and favourable environmental conditions

DNA damage checkpoints (late G1 and G2) - checks for DNA damage before replication (G1) and checks for damaged or unduplicated DNA (G2)

Metaphase checkpoint - checks for chromosome attachment to mitotic spindle

Question 23

Cell cycle progression is determined by the presence of which factors

Answer 23

Growth factors

Question 24

What is the restriction factor

Answer 24

The point in which the cell no longer requires growth factors to complete the cell cycle and commits to cell division

Question 25

Which cyclin is required for progression from G1 to restriction point

Answer 25

Cyclin D

Question 26

How long before initiation of S phase is cyclin D

Answer 26

2-3 hours before

Question 27

Which protein acts as a gatekeeper at the restriction point

Answer 27

Retinoblastoma (Rb) protein

Question 28

What is epidermal growth factor involved in (EGF)

Answer 28

Re-epithelialisation

Question 29

What is platelet derived growth factor (PDGF)

Answer 29

Matrix formation (>fibroblasts+migration) and remodelling (production of proteases)

Question 30

Vascular endothelial growth factor

Answer 30

Angiogenesis (endothelial cell>+migration)

Question 31

What happens when growth factor increases at restriction point

Answer 31

Growth factor activates CDK-Cyclin 4/6D

This causes phosphorylation of Rb protein which stops the inhibition of the transcription factor E2F

Gene transcription occurs

mRNA translation occurs

Enzymes and other proteins are produced that are involved in S phase

Question 32

What do tumour supressor genes do?

Answer 32

They act as the ‘brakes of the cell; they encode cell proteins that inhibit cell growth and proliferation to maintain the integrity of the genome
This causes cell cycle arrest in abnormally dividing cells and repair DNA damage

Question 33

3 examples of tumour suppressors

Answer 33

Rb –> blocks entry to mitosis
p53 –> detects DNA damage
BRCA1 –> DNA repair

Question 34

What can cause damage to DNA

Answer 34

Chemical mutagens, radiation, errors in replication

Question 35

Rb =

Answer 35

blocks entry to M

Question 36

p53 =

Answer 36

detects DNA damage

Question 37

What type of factor is p53

Answer 37

A transcription factor

Question 38

What does p53 do

Answer 38

Inhibits cell cycle progression if DNA damage has occurred, which can cause cell cycle arrest and then apoptosis OR DNA repair

Question 39

If levels of p53 is too low which other tumour suppressor does this causes the expression of

Answer 39

p21

Question 40

Which checkpoints involve p53/23

Answer 40

Late G1 and late G2

Question 41

What happens at the spindle assembly checkpoint

Answer 41

Checks whether chromosomes are attached to the spindle

Question 42

What happens if chromosomes aren’t attached to spindles

Answer 42

Anaphase is inhibited, anaphase promoting complex is inhibited until all chromosomes are attached, once they are, anaphase inhibition is alleviated