Cell regulation

Question 1

1st checkpoint

Answer 1

during G1, DNA damage checkpoint: checks for damaged DNA before the cell enters S phase

Question 2

2nd checkpoint

Answer 2

DNA replication checkpoint: checks for the presence of unreplicated DNA at the end of G2 before the cell enters mitosis

Question 3

3rd checkpoint

Answer 3

spindle assembly checkpoint: checks for all chromosomes being attached to the spindle before the cell progresses with mitosis

Question 4

cyclins

Answer 4

bind to and activate cyclin-dependent kinases (CDK) to control progression through the cell cycle

Question 5

cyclin-CDK complexes

Answer 5

phosphorylate target proteins
that promote cell division

Question 6

M cyclin–CDK

Answer 6

helps prepare the cell for mitosis

Question 7

S cyclin–CDK

Answer 7

helps initiate DNA synthesis

Question 8

G1/S cyclin–CDK complex

Answer 8

prepares cell for DNA replication

Question 9

p53

Answer 9

• a protein found in the nucleus
• DNA damage activates protein
  kinases that phosphorylate p53
• phosphorylated p53 turns on genes that
  inhibit the cell cycle
• inhibiting the cell cycle gives the cell
  time to repair the damaged DNA or trigger
  cell death

Question 10

oncogene

Answer 10

cancer-causing gene

Question 11

proto-oncogenes

Answer 11

normal genes that have the potential to become cancerous if mutated

Question 12

tumor suppressors

Answer 12

genes that encode proteins whose normal activities inhibit cell division