Lecture 3: Phases of Cell Growth and Division

Question 1

The “point of no return” at the border of G1 and S1.

Answer 1

Restriction Point (R)

Question 2

What point in the cell cycle is the cell’s only chance to reset itself if it lacks the size, energy, etc. needed for division?

Answer 2

The restriction point (R)

Question 3

Which tumor suppressor regulates the restriction point and sends the cell cycle back to the beginning if the cell is not ready for division?

Answer 3

Rb

Question 4

Which phases in the cell cycle make up interphase?

Answer 4

G1, S, and G2

Question 5

What happens during G1 (gap phase I) of the cell cycle?

Answer 5

Cells grow larger, copy organelles, and synthesize macromolecules.

Question 6

During which phase of the cell cycle do cells synthesize a complete copy of their DNA and make a duplicate centrosome?

Answer 6

S phase

Question 7

What happens during G2 (gap phase 2)?

Answer 7

The cell grows more, makes more proteins and organelles, and prepares for mitosis.

Question 8

Which tumor suppressor regulates whether or not the cell undergoes DNA replication?

Answer 8

Rb

Question 9

Which tumor suppressor regulates the fidelity of the genome?

Answer 9

p53

Question 10

Where is the second checkpoint in the cell cycle located? What does it check for?

Answer 10

On the G2/M border; it checks for DNA replication errors.

Question 11

Which tumor suppressor regulates the G2/M border?

Answer 11

p53

Question 12

If errors are found in the DNA replication at the G2/M checkpoint, what options does the cell have?

Answer 12

1) Fix the errors

2) Apoptosis

Question 13

What kind of tumor suppressor is p16?

Answer 13

It is an INK4 tumor suppressor protein

Question 14

How does p16 (INK4) stop cell division?

Answer 14

If inactivates the Cdk4 and cyclin D1 complex, thereby activating Rb, which in turn inactivates E2F transcription factor/oncogene, stopping cell division by preventing the entrance of the cell into S phase.

Question 15

What happens in the cell cycle if the Cdk4 and cyclin D1 complex is active?

Answer 15

The Cdk4/cyclin D1 complex will inactivate Rb, thereby activating the E2F transcription factor, which allows entrance of the cell into S phase and continues the process of preparing for cell division.

Question 16

How does INK4 (p16) indirectly activate Rb?

Answer 16

By inactivating the Cdk4/cyclin D1 complex that would otherwise inactivate Rb.

Question 17

What does CDKs stand for?

Answer 17

Cyclin dependent kinases

Question 18

What is the name for the regulatory protein that binds to a CDK to activate it?

Answer 18

cyclin

Question 19

Which cyclin interacts with CDK4 to take a cell through G1 and into S phase?

Answer 19

Cyclin D

Question 20

Which CDK interacts with cyclin D to take a cell through G1 and into S phase?

Answer 20

CDK4

Question 21

Which cyclin interacts with CDK2 to take a cell from G1 into S phase?

Answer 21

Cyclin E

Question 22

Which CDK interacts with cyclin E to take a cell from G1 into S phase?

Answer 22

CDK2

Question 23

Which cyclin interacts with CDK2 to take the cell through S phase and into G2?

Answer 23

Cyclin A

Question 24

Which CDK interacts with cyclin A to take the cell through S phase and into G2?

Answer 24

CDK2

Question 25

Which cyclin interacts with CDK1 to take the cell from G2 into M (mitosis)?

Answer 25

Cyclin B

Question 26

Which CDK interacts with cyclin B to take the cell from G2 into M (mitosis)?

Answer 26

CDK1

Question 27

What are three ways to mutate DNA?

Answer 27

1) Intrinsic
2) Exposure to chemical agents
3) Radiation

Question 28

How can a cell be mutated intrinsically?

Answer 28

1) Spontaneous base modifications

2) Replication errors

Question 29

What types of chemical agents can mutate DNA?

Answer 29

1) Endogenous agents (oxygen radicals)

2) Exogenous agents (chemical mutagens)

Question 30

What types of radiation can mutate DNA?

Answer 30

1) Ultraviolet radiation

2) Ionizing radiation

Question 31

Which structures cause a lot of DNA damage during mitosis?

Answer 31

Centrosomes

Question 32

What is it called when there are centrosomes pulling DNA in different directions from multiple poles?

Answer 32

Centrosome amplification

Question 33

___________ can drive centrosome amplification.

Answer 33

Oncogenes

Question 34

Why are the damages caused to DNA by centrosome amplification preserved in the next replication cycle?

Answer 34

Because in the next cycle, the centrosomes coalesce at just two poles, preserving the rearrangement and stabilizing the genome (and thereby passing on mutations).

Question 35

What is ARF?

Answer 35

a tumor suppressor

Question 36

When is ARF activated?

Answer 36

When it senses too much oncogene signaling.

Question 37

True or false: Oncogenes inhibit ARF.

Answer 37

False; oncogenes turn the ARF tumor suppressor on.

Question 38

What does ARF do when it senses oncogene signalling?

Answer 38

Shuts down growth.

Question 39

If the E2F oncogene is active, what will happen normally?

Answer 39

It will be sensed and shut down by ARF.

Question 40

Which tumor suppressor regulates cell arrest and apoptosis?

Answer 40

p53

Question 41

Which tumor suppressor senses DNA damage and alerts p53?

Answer 41

ATM

Question 42

What does ATM do when it senses DNA damage?

Answer 42

Tells p53 if the damage can be repaired and, if so, sits at the break site and tells the repair machinery where to go.

Question 43

What are two ways by which apoptosis takes place?

Answer 43

1) Extrinsic (by death receptors)

2) Intrinsic (through the mitochondria)

Question 44

The degree to which a gene or set of genes is expressed in an individual’s phenotype.

Answer 44

Penetrance

Question 45

To be penetrant, a mutation must affect one of these 4 things:

Answer 45

1) RNA stability (so that DNA can’s become a protein)
2) Disrupt the critical binding region of a protein (so the protein can’t perform the same function).
3) Make shorter proteins (change the protein’s function)
4) Point mutations (affects the function of the proteins)