Cell Replication

Question 1

What are the phases of the cell cycle?

Answer 1

G0
G1
S
G2
M

Question 2

Which phases take place during interphase state?

Answer 2

G1+S+G2

Question 3

In which phase does DNA replication occur?

Answer 3

S Phase (interphase)

Question 4

In which phase does mitosis occur?

Answer 4

M Phase

Question 5

What is G0 Phase?

Answer 5

Gap, no cell division

Question 6

What happens at G1 checkpoint?

Answer 6

Checked if environment favours cell replication

Question 7

What happens at G2 checkpoint?

Answer 7

Checked if all DNA is replicated and no DNA damage is present

Question 8

What happens at M checkpoint?

Answer 8

Checked if all chromosomes are properly attached to the spindle and ready for cell cleavage

Question 9

What happens if G2 checkpoint is not passed?

Answer 9

DNA repair or Apoptosis

Question 10

What stimulates the cells in G0 phase to enter G1 phase?

Answer 10

Growth factors

Question 11

What is c-Myc?

Answer 11

a transcription factor that stimulates the expression of cell cycle genes (also proto-oncogene)

Question 12

What is the likely outcome of overexperssion of c-Myc?

Answer 12

Tumour growth

Question 13

What is Cdk and which cells would have it?

Answer 13

Cyclin dependent kinase found in. proliferating cells

Question 14

When is Cdk active, what does it do?

Answer 14

Active when cyclin is present, carries out phosphorylation of proteins

Question 15

Which amino acids are substrates for Cdk and why?

Answer 15

Serine, tyrosine and threonine as they all have hydroxyl groups

Question 16

Why are cyclins boh produced and degraded at the same time?

Answer 16

Different cyclins with different concentrations at different times to control the cell cycle

Question 17

Put the molecules in order to make cascade: Cdk 4/6:cyclin D complex, cyclin D, growth factors, c-Myc

Answer 17

Question 18

What do the checkpoints check for in the cell (generalised)?

Answer 18

Question 19

What are the advantages of kinase-kinase regulations?

Answer 19

Signal amplification
Diversification
Opportunity for regulation
(reversal by phosphatases)

Question 20

What are the names of Cdk molecules present in proliferating cells?

Answer 20

Cdk 1, 2, 4, 6

Question 21

What are the names of cyclins transiently expressed at specific points in the cell cycle?

Answer 21

Cyclin A, B, D, E

Question 22

How is Cdk activity regulated?

Answer 22

Interaction with cyclins
Phosphorylation

Question 23

How is a Cdk:cyclin complex activated?

Answer 23

Through phosphorylation and removal of inhibitory phosphate

Question 24

What kind of feedback does the active Cdk provide?

Answer 24

Positive feedback for activation or inhibiton of kinases

Question 25

What are the 2 types of cyclins?

Answer 25

S cyclin (for Interphase) M cyclin (for Mitosis)

Question 26

What is the degradation mechanism of cyclins?

Answer 26

Ubiquitination/ubiquitylation tags cyclins for degradation in proteasome

Question 27

What is the order of Cdk:cyclin complexes activated sequntially starting from stimulation by c-Myc?

Answer 27

4/6:D 2:E 2:A 1:B

Question 28

What is the role of Retinoblastoma (Rb) protein?

Answer 28

Tumour supression - inactivating transcription factors

Question 29

How is Rb protein inactivated?

Answer 29

Through phosphorylation

Question 30

What is E2F and how does it contribute to the cell cycle?

Answer 30

E2F is a transcription factor and regulates the expression of several genes need for cell cycle progression - can be inactivated by Rb

Question 31

What causes DNA damage?

Answer 31

X-rays

Question 32

What is Rb protein named after?

Answer 32

Eye tumour in children caused by inactive or missing Rb

Question 33

Which protein is activated in case of DNA damage and how?

Answer 33

p53 is activated through phosphorylation by protein kinase

Question 34

How does p53 interfere with the cell cycle?

Answer 34

Upregulates production of p21 which inhibits cdk:cyclin complexes

Question 35

What happens to active p53 in absence of DNA damage?

Answer 35

Degraded in proteasome

Question 36

Which oncogenes are overly expressed in breast cancer?

Answer 36

EGFR/HER2 and/or Cyclin D1

Question 37

What does the overexpression of EGFR/HER2 result in?

Answer 37

Breast cancer

Question 38

What is the treatment for HER2+ metastatic breast cancer?

Answer 38

Herceptin antibodies

Question 39

What is Ras?

Answer 39

An oncogene - mutationally activated in many cancers (e.g. pancreatic, lung, colorectal, thyroid)

Question 40

What does the overexpression of Cyclin D1 result in?

Answer 40

Breast cancer

Question 41

What is the cause of 80% of small cell lung cancers?

Answer 41

loss of function in mutated Rb protein

Question 42

What is the cause of 50% of all human cancers?

Answer 42

loss of function in mutated p53