The Embryo: Cell Cycle II

Question 1

What happens if there are no checkpoints in cell cycle?

Answer 1

Uncontrolled cell growth

Hyperplasia - increased number of cells in organ or tissue
» Neoplasia - formation of abnormal growth tissue

Question 2

What are the important cdki?

Answer 2

Associated with the G phases (1 and 2)

p16 - inhibits cdk4/6

p21 - inhibits cdk2

Question 3

How is the G2/M growth phase regulated?

Answer 3

cdk1 is inactivated by Wee1 kinase

Activated by cdc25 phosphate for M entry

Question 4

How is M phase regulated?

Answer 4

At metaphase-anaphase transition

Anaphase promoting complex (APC)

Question 5

What does the Anaphase promoting complex do?

Answer 5

If conditions are favorable:

Promote degradation of cyclins
to deactivate cdk1

This deactivations triggers entry into anaphase and telophase

Question 6

What is G0 phase?

Answer 6

Resting phase that signals to stop growth

Stop expression of cdks, cyclins, etc

Question 7

How do cells detect DNA damages?

Answer 7

ATM/ATR

ATM kinase: bind to DNA double strand breaks

ATR kinase: bind to single strand breaks

Question 8

How do ATM/ATR stop the cell cycle?

Answer 8

Phosphorylating chk1 and chk2 that cause

      1. Activation of p53 to cause the transcription of p21
     2. Inactivation of cdc25

Note: associate with G1/S and G2/M down regulation (promotes whatever stops the transition)