6

Question 1

FtsZ

Answer 1

gene that encodes binary fission

Question 2

cyclins

Answer 2

proteins synthesised to activate kinases; levels rise and fall with each turn of the cell cycle
Once activated by cyclins, the kinases phosphorylate target proteins involved in promoting cell division
These kinases are called cyclin-dependent kinases (CDKs) and are always present in the cell but only active when bound to the appropriate cyclin
Kinase activity of cyclin-CDK complexes trigger the required cell cycle events

Question 3

G1/S cyclin- CDK complex

Answer 3

active at end of G1 phase, necessary for cell to enter S phase
Activates a protein that promotes the expression of histone proteins needed for packaging the newly replicated DNA strands

Question 4

S cyclin-CDK complex

Answer 4

necessary for the cell to initiate DNA synthesis
Activates enzymes and other proteins necessary for DNA replication
Once replication has begun at DNA, S cyclin-CDK activity prevents the replication proteins from reassembling at the same place and re-replicating the same DNA sequence (which could cause cancer or cell death)

Question 5

M cyclin-CDK complex

Answer 5

initiates multiple events associated with mitosis
Phosphorylates structural proteins in the nucleus, triggering the breakdown of the nuclear envelope in pro metaphase
Phosphorylates proteins that regulate the assembly of tubulin into microtubules, forming mitotic spindle

Question 6

p53

Answer 6

When DNA is damaged by radiation, a specific protein kinase is activated that phosphorylates a protein called p53
Phosphorylated p53 binds to DNA, where it turns on the expression of several genes
One of these genes codes for a protein that binds to and blocks the activity of the G1/S cyclin-CDK complex
P53 arrests the cell at the G1/S transition, giving the cell time to repair the damaged DNA

Question 7

oncogene

Answer 7

help cell progress through cell cycle