Cell Cycle

Question 1

What can help control the cell cycle

Answer 1

rounds of protien degredation and protien synthesis that either move the cycle forward or stop it

Phosphorylation events

Regulatory protiens

Question 2

What are some key regulatory protiens of the cell cycle

Answer 2

Tumor suppressors and oncogenes (tumor causing)

Question 3

What are the two phases in the cell cycle

Answer 3

S phase: dna synthesis where the genome is replicated

M phase: mitotic phase where the chromosomes get separated to daughter cells

Question 4

How can the s phase (dna replication) be monitored

Answer 4

By adding in 3HT

if the length of the cell cycle is known, the length of that s phase can be calculated by the percent of cells labeled with 3HT

IDK

Question 5

How can dna be analyzed with a fluorescence activated cell shorter (FACS)

Answer 5

The cells are stained with a dye called propidium iodide the floureces when the cell bind to dna

The amount of flourense is equal to the amount of dna in the cell

IDK

Question 6

Slide 10

Answer 6

Idk

Question 7

How is entry of the cell into the M PHASE triggered

Answer 7

By a protein kinase called the maturations promoting factor (MPF)

Question 8

What is the MPF

Answer 8

It has two subunits

A kinase and a regulatory cyclin subunit

When there’s higher cyclin concentration, the kinase if the MPF is activated

This drives mitosis forward

Question 9

What happens when cyclin is low

What if high

Answer 9

Low, the MPF kinase doesn’t have the cyclin subunit, it’s inactive

High, the MPF kinase has the cyclin subunit, it’s activated and entry to mitosis starts

Question 10

What type of cells is MPF in

Answer 10

Mammalian

Question 11

At what two points is the cell cycle controlled in yeast cells

Answer 11

The START (between g1 and S) and G2-m transition

Question 12

In yeast cells what activated the cell cycle

Answer 12

The same kinase: cdk(also called cdc2)

Two different cyclin for the two diff points of control (g1/s cyclin and mitotic cyclins)

Question 13

Explain how the activation of the cell cycle happens in yeast cells

Answer 13

Intially g1/s cyclins are produced and a complexing with the cdk

This activates the cell cycle

Eventually, the g1/s cyclins get degraded and the new mitotic cyclins complex with cdk to promote mitosis

Eventually these mitotic cyclins drop off again at the end of m phase

So basically round of cyclin degradation and synthesis control the cycle

Question 14

What is used to activate and deactivate the kinases to control the cell cycle

Answer 14

CAK
WEE1
cdc25

Question 15

What is CAK

Answer 15

Cdc activating kinase

It adds a phosphate to the thr161 on the cdk subunit to activate it

Question 16

What is WEE1

Answer 16

A cdc inhibiting kinase

It adds a phosphate to the tyr15 to deactivate the kinase and stop mitosis

Cell is not wee anymore since not splitting

Question 17

What is cdc25

Answer 17

A phosphatase

It removes the inhibitory phosphate from tyr15 on the cdk

This is the step that drive mitosis forward

Question 18

What is cyclin d1

Answer 18

A cyclin that is made from the mapk pathway

Its key to start the cell cycle and is present in g1

Question 19

What is special about the cdks and their cyclins

Answer 19

There a many different cyclins and specific pairings of these cycling to the cdks

Question 20

What is the effect of a anticancer drugs on the cdks and cyckins

Answer 20

The drugs inhibit the cdk4 and cdk6 in the g1 phase

Question 21

What is the retinoblastoma protien (pRB)

Answer 21

Protien that Controls the cell cycle

Represses the genes needed for S phase to start

If mutated there is abnormal cancer growth, so it is a tumor suppressor

Question 22

when is pRB phosphorylated/dephisphorylated

When is it inhibited and activated

Answer 22

Phosphorylated: at end of G1
De: at end of m phase

Inhibited when phosphorylated,
Activate when dephosphorylated

Question 23

Describe how pRB represses genes for a phase

Answer 23

In g1, the transcription factor E2F is bound to pRB

This is all at the promoter in the dna and represses the gene

Once CDK is activated, it phosphorylates pRB and the inactive pRB is released from E2F

The lone E2F on the dna turns into an activator and is now able to transcribe dna for s phase

Question 24

What happens to E2F once the s phase is over

Answer 24

The pRB goes back to E2F to repress s phase until it’s needed again

Question 25

What is the cell cycle order

Answer 25

G1
S
G2
M

Question 26

How can progression through the s phase get inhibited?

Answer 26

By p27 a cdk inhibitor

Question 27

What does p27 do to stop the s phase and inhibit the cdk

Answer 27

It forms a trimeric complex with CycA and CDK2 (the cdk and cyclin for the s phase ) this inhibits the cdk and cyclin

This stops the activity of the cdk so s phase doesn’t progress

Question 28

What happens if p27 is eliminated

Answer 28

Cell cycle happens more and excess cell proliferation occurs

Also excess organ growth in micr

Question 29

Slide 20

Answer 29

Okay