10.3

Question 1

G1/S checkpoint

Answer 1

 Cell “decides” to divide
 Primary point for external influence

Question 2

G2/M checkpoint

Answer 2

 Cell makes a commitment to mitosis
 Assesses success of DNA replication

Question 3

M/Spindle checkpoint

Answer 3

Cell ensures that all chromosomes are attached to the spindle

Question 4

Explain the role of Cdks in the cell cycle control system

Answer 4

o Partner with different cyclins at different points in the cell cycle
o Phosphorylate proteins at 2 sites
 At one site, inactivates Cdk when cyclin is not attached
 At another site, activates Cdk if cyclin is attached

Question 5

Characterize the role of the anaphase-promoting complex in mitosis.

Answer 5

o To trigger anaphase itself
 Marks securing for destruction; no inhibition of separase; separase destroys cohesion
 If you don’t have APC, you will never get ride of cohesion and will never be able to separate the sister chromatids
 APC/C
* Active form
* Indicates cyclin attachment

Question 6

Outline the role of growth factors in driving cellular proliferation

Answer 6

Growth factors act as ligands to activate signaling pathways to ultimately turn on the expression of cell cycle regulator genes (such as CDKs)

Question 7

proto-oncogenes genes in driving cancer

Answer 7

 Normal cellular genes that become oncogenes when mutated
* Oncogenes can cause cancer
 Most encode for proteins that drive cellular proliferation
* Ex
o Growth factor receptors
o Ras protein
o Src kinase
 Only 1 copy needs to undergo mutation for uncontrolled division to take place

Question 8

tumor-suppressor genes in driving cancer

Answer 8

 Normal cellular genes that function to control the cell cycle
* Job is to inhibit
 Both copies must lose function
* If only 1 copy is mutated then the normal copy can still regulate the cell cycle