A8

Question 1

Cells in the G0 state:

1.	 cannot re-enter the cell cycle

2.	 have duplicated their DNA

3.	 have entered from G1 or G2 checkpoints

4.	 do not divide

Answer 1

4`

Question 2

Cell proliferation genes can become oncogenes by (select all correct options that apply)

Gene amplifications

Activating point mutations

Inactivating point mutations

Chromosomal translocations

Answer 2

a, b, d

Question 3

Which of the following mutations is likely to prevent normal cell-cycle progression?

1.	 A mutation in a cell-surface mitogen receptor that made it active even in the absence of its mitogen ligand

2.	 A mutation that allowed the kinase subunit of the G1-Cdk complex to be active independent of its phosphorylation status.

3.	 A mutation that prevented binding of Rb to gene regulatory proteins.

4.	 A mutation that destroyed the kinase activity of the S-cyclin-Cdk complex

Answer 3

4

Question 4

A stem cell divides into two daughter cells and one of the daughter cells goes on to become a terminally differentiated cell. What is the typical fate of the other daughter cell?

1.	 The other daughter cell becomes terminally differentiated

2.	 The other daughter cell typically remains a stem cell

3.	 The other daughter cell migrates to a different tissue.

4.	 The other daughter cell dies

Answer 4

2

Question 5

Levels of cyclin-dependent kinase (Cdk) activity change during the cell cycle as a result of…

1.	 the Cdks activating the cyclins

2.	 the Cdks binding different cyclins to become active

3.	 the Cdks phosphorylating each other

4.	 the level of production of Cdks changing throughout the cell cycle

Answer 5

2

Question 6

When mammalian cells are irradiated, they stop dividing and arrest at a G1 checkpoint. Which is the event that occurs last in this process?

1.	 Production of p21

2.	 Inactivation of cyclin-Cdk complex

3.	 Activation of p53

4.	 DNA damage

Answer 6

2

Question 7

During intrinsic apoptosis

1.	 The p53 tumour suppressor protein activates pro-survival factors

2.	 Cytochrome c is released from mitochondria

3.	 Caspases undergo cleavage to become inactivated

4.	 Pro-survival factors open pores in the outer mitochondrial membrane

Answer 7

2