Ch 9 Lecture (Replication)

Question 1

replication is confined to the … phase

Answer 1

S phase

Question 2

the G1-S checkpoint is also known as the

Answer 2

restriction point
start

Question 3

in order to pass through the start checkpoint, the cell must

Answer 3

have a certain minimum amount of growth and have no DNA damage

Question 4

four steps of checkpoint passage

Answer 4

1. Cell must express the correct growth factor receptor
2. Cell must have growth factor present to bind to the receptor
3. Cell must receive continued growth factor signal long enough to trigger the production of active cyclin proteins
4. Cyclin proteins must activate a set of enzymes called cyclin-dependent kinases

Question 5

signal from cell membrane receptor to the nucleus is mediated by

Answer 5

signal transduction pathways

Question 6

components of signal pathways are also called

Answer 6

proto-oncogenes

Question 7

Cell must receive continued growth factor signal long enough to trigger the production of

Answer 7

active cyclin proteins

Question 8

Cdk

Answer 8

cyclin-dependent kinases

Question 9

tumor suppressor genes

Answer 9

Genes whose products prevent the activation of CdK enzymes when criteria have not been met

Question 10

examples of tumor suppressor genes

Answer 10

Rb and p53

Question 11

Rb is usually found in an

Answer 11

active, unphosphorylated form

Question 12

Rb control steps

Answer 12

1. With continued growth factor signal, G1-Cdk (Cyclin D-Cdk) activity is stimulated
2. Active G1-Cdk will phosphorylate Rb
3. Phosphorylated Rb will be inactivated and release the transcription factor E2F
4. E2F will activate the transcription of genes required for entry into S phase
5. Downstream components participate in positive feedback of E2F

Question 13

what does p53 do

Answer 13

Prevents passage through checkpoint if DNA damage has occurred

Question 14

Transcription of p53 is … by growth factor signal in preparation for restriction point decision

Answer 14

upregulated

Question 15

activity of p53 is under negative regulation by

Answer 15

Mdm2

Question 16

how does Mdm2 work with p53

Answer 16

Transcription of Mdm2 is upregulated by p53
Binds to p53 and targets it to degradation pathways
Also binds to p53 and inhibits its function as a transcriptional activator

Question 17

p53 after DNA damage

Answer 17

p53 and Mdm2 are phosphorylated
Mdm dissociates from p53
p53 degradation is decreased
p53 translocates to the nucleus and activates the expression of genes that repress cell cycle progression

Question 18

Rb and p53 are

Answer 18

negative effectors of cell cycle progression

Question 19

p21

Answer 19

Expressed as a result of DNA damage and p53 activity
Binds to cyclin/CdK complexes needed for Rb inactivation

Question 20

order of tumor suppressors

Answer 20

p53-p21
p27
Rb