WEEK 2

Question 1

What is cell proliferation?

Answer 1

the process by which a cell grows and divides to produce two daughter cells, leads to exponential increase in cell number

Question 2

What is the fundamental basis of cell proliferation?

Answer 2

New cells must be identical therefore growth and division process (cell cycle) must be tightly controlled

Question 3

How is the cell cycle controlled?

Answer 3

Checkpoints and feedback control

Question 4

Give the stages of the cell cycle

Answer 4

G1 phase->growth and preparation for DNA replication
S (synthesis) phase->DNA replication
G2 phase->growth and preparation for mitosis
M (mitosis) phase->chromosome segregation, cell division, cytokinesis

Question 5

What is cytokinesis?

Answer 5

Cytoplasmic division after mitosis, forming 2 daughter cells with similar amount of nuclear DNA and organelles

Question 6

What are cell cycle checkpoints?

Answer 6

Critical control points where stop and go-ahead signals can regulate the cell cycle

Question 7

What are the three major checkpoints?

Answer 7

G1, G2 and M checkpoints

Question 8

Describe the G1 checkpoint (restriction point)

Answer 8

ensures cell is large enough and contains enough nutrients to divide. if cell doesn’t receive go-ahead signal at this point, it will exit the cell cycle and switch to a non-dividing state (G0)

Question 9

Describe the G2 checkpoint

Answer 9

ensures DNA replication in S phase is completed successfully

Question 10

Describe the Metaphase checkpoint

Answer 10

ensures all chromosomes are attached to mitotic spindle by a kinetochore

Question 11

What occurs if there’s failure at any of these checkpoints?

Answer 11

Apoptosis-induced cell death

Question 12

What enzymes regulate the cell cycle?

Answer 12

Cyclin-dependent kinases (CDKs)-G1, G2 and M CDKs

Question 13

How are CDKs activated?

Answer 13

Phosphorylation due to Cyclin binding-a molecule which’s fluctuations indicate a need for new cells in a specific area

Question 14

How do CDKs regulate the cell cycle?

Answer 14

They activate and encourage the continuation of the cell cycle to proliferation

Question 15

What is a kinase?

Answer 15

A protein which activates or deactivates another protein by phosphorylating them

Question 16

When do cyclins accumulate and what effect does this have on mitosis?

Answer 16

During G1, S and G2 phases, leading to enough cyclin available by the end of G2 checkpoint to form M-CDK complexes initiating mitosis

Question 17

How does M-CDK switch itself off?

Answer 17

Initiating a process which leads to cyclin destruction

Question 18

Which cyclin-CDKs are required at the restriction point?

Answer 18

CDK4/cyclin D and CDK2/cyclin E/A

Question 19

Which cyclin-CDKs are required at the Metaphase checkpoint?

Answer 19

CDK1/cyclin A/B

Question 20

What regulates the restriction point?

Answer 20

Retinoblastoma protein (pRB) which is a tumour suppressor protein

Question 21

How does pRB regulate the restriction point?

Answer 21

In absence of growth factors, pRB binds to transcription regulators of genes for cell proliferation, preventing cell cycle continuation
Growth factor presence causes activation of G1 and G1/S CDKs which phosphorylate pRB and cause its release from transcription regulators, activating genes for cell proliferation

Question 22

What regulates the DNA damage checkpoint (G1/S phase)?

Answer 22

p53 which is a tumour suppressor protein

Question 23

How does p53 regulate the DNA damage checkpoint?

Answer 23

p53 increases due to DNA damage, activating transcription of p21, an inhibitor of CDK, preventing continuation into S phase, giving time for DNA repair

Question 24

What happens if DNA damage is too severe?

Answer 24

p53 can induce apoptosis

Question 25

What occurs due to a loss of function mutation?

Answer 25

Unrestrained replication of damaged DNA, leading to genomic instability/resistance to apoptosis

Question 26

What are the consequences of checkpoint failure?

Answer 26

Proliferation of cells in absence of growth factors, replication of damaged DNA, segregation of incompletely replicated chromosomes, divisions of cells with wrong number of chromosomes->leads to genomic instability and increased rate of mutation

Question 27

Hallmarks of cancer are

Answer 27

Sustaining proliferative signalling
Evading growth suppressors
Activating invasion and metastasis
Enabling replicative immortality
Inducing angiogenesis
Resisting apoptosis

Question 28

Stages of a growth factor signalling pathway

Answer 28

membrane receptor activation leads to dimerisation and phosphorylation, adapter protein binds to phosphorylated receptor in cytoplasm, Ras (G-protein) binds to adaptor, signalling cascade, phosphorylation of gene regulatory proteins, expression of proliferative genes

Question 29

Define oncogenic

Answer 29

pertaining to the origin or development of tumours or cancer

Question 30

What is the result of receptor becoming oncogenic?

Answer 30

deregulated cell proliferation due to mutated/constitutively active/over-expressed receptor causing signalling pathway occurrence without presence of growth factor

Question 31

What is the result of signalling proteins becoming oncogenic?

Answer 31

deregulated cell proliferation without activation of receptor due to mutated/constitutively active Ras/Kinase proteins

Question 32

What is the result of regulatory proteins becoming oncogenic?

Answer 32

deregulated cell proliferation due to over-expression of transcription factors

Question 33

LOOK OVER NOTES ON:

Answer 33

Metabolism and its control (1) and Appearance and Classification of Epithelial tissue (+histology)