Tumours 4

Question 1

What is the order of the cell cycle starting from M?

Answer 1

M, G1, S, G2 and back to M

Question 2

Which parts of the cell cycle make up the interphase (longest part)?

Answer 2

G1, S, G2

Question 3

What is G0?

Answer 3

Resting mode of the cell

Question 4

what process in the cell cycle ensures each cell receives a full chromosome complement and does not have any mutations?

Answer 4

Quality control check

Question 5

What can be the outcomes if there is a problem with the cell and it doesn’t pass the quality control? (2)

Answer 5

1. DNA is fixed/ repaired

2. apoptosis occurs

Question 6

what are some external factors which affect cell cycle control?

Answer 6

• hormones
• growth factors
• cytokines
• stroma (connective tissue cells)

Question 7

What intrinsic factors can affect cell cycle control?

Answer 7

• critical checkpoints (restriction point)

- after restriction point, progression becomes autonomous (cell controls itself)

Question 8

what occurs in G1 phase? (2)

Answer 8

• cell increases in size

- G1 checkpoint ensures everything is ready for DNA synthesis

Question 9

what occurs in S phase?

Answer 9

DNA replication occurs

Question 10

What occurs in G2 phase? (2)

Answer 10

• cell continues to grow

- checkpoint ensures that everything is ready to enter the M phase

Question 11

what chemicals are present at checkpoints?

Answer 11

cyclically active and inactive enzymes

Question 12

What are catalytic subunits activated by?

Answer 12

Regulatory subunits

Question 13

What are catalytic subunits called?

Answer 13

Cyclin-dependent kinases (CDKs)

Question 14

what are regulatory sub-units called?

Answer 14

Cyclins

Question 15

What is the active enzyme complex called in the cell cycle?

Answer 15

CDK/cyclin complex

Question 16

What do active CDK/cyclin complexes do?

Answer 16

Phosphorylate proteins (which results in activation or inactivation of substrates)

Question 17

What form are CDKs constitutively expressed in?

Answer 17

Inactive form

Question 18

What does CDK need to become activated?

Answer 18

Cyclins

Question 19

what kind of phosphorylation occurs at pRb?

Answer 19

hypophosphorylation

Question 20

what happens to phosphorylation as cell progresses through the cycle?

Answer 20

increases

Question 21

what phosphorylates pRb?

Answer 21

active cyclin D/CDK complexes

Question 22

What happens to the cell cycle when it stops? (in terms of pRb and E2F)

Answer 22

• pRb is active (hypophosphorylated)

- inactive E2F

Question 23

What happens to the cell cycle when it goes ahead? (in terms of pRb and E2F)

Answer 23

• inactive pRb ( phosphorylated)

- active E2F

Question 24

What activates vital target genes in the cell cycle?

Answer 24

free E2F transcription factor

Question 25

What is the E2F factor?

Answer 25

Stimulator of cell cycle entry

Question 26

What does active pRb do to the cell cycle?

Answer 26

Puts a brake on the cell cycle (stops it)

Question 27

What 3 factors are affected which cause a cell to lose control of its proliferation?

Answer 27

1. cell division 2. apoptosis 3. DNA repair

Question 28

What 3 non-lethal genetic damage can cause carcinogenesis?

Answer 28

1. chemicals 2. radiation 3. oncogenic viruses

Question 29

what does chemical carcinogenesis cause in DNA on a molecular level?

Answer 29

purine and pyrimidine bases in DNA are critically damaged by various oxidising and alkylating agents

Question 30

What is formed as a result of chemical carcinogenesis on particular chromosome sites?

Answer 30

Adduct formation (DNA adducts)

Question 31

What does radiation carcinogenesis cause in DNA on a molecules level?

Answer 31

purine and pyrimidine bases in DNA are critical cellular targets for radiation damage

Question 32

What are 3 examples of harmful radiation?

Answer 32

1. UV present in sunlight 2. X rays 3. gamma radiation

Question 33

what are the 2 regulatory pathways which are frequently disrupted?

Answer 33

1. cyclin D-pRB-E2F pathway (absent or inactive pRb releases cell cycle brake and E2F is activated which causes proliferation) 2. p.53 pathway (which is a tumour suppressor)

Question 34

What does p.53 do?

Answer 34

tumour suppressor

Question 35

What are the 4 genes which often have mutations causing cancers?

Answer 35

1. Rb 2. CDK4 3. cyclin D 4. p.16 (tumour suppressor gene)

Question 36

What happens to the level of p.53 in damaged cells?

Answer 36

increases

Question 37

Why is p.53 increased in damaged cells?

Answer 37

- facilitates DNA repair | - induces cell cycle arrest at G1 and apoptosis

Question 38

What happens if there is a mutation to p.53 gene?

Answer 38

- cells do not arrest at G1 or repair damaged DNA | - cells proliferate and form malignant neoplasm (uncontrollable cell division)