Putting It All Together: The Cell Cycle

Question 1

The cell cycle can be divided into interphase and ______________.

Answer 1

Mitosis

Question 2

What 3 stages make up interphase?

Answer 2

G1

S

G2

Question 3

What occurs during G1 of interphase?

Answer 3

Cellular contents of cell, excluding chromosomes, are duplicated

Question 4

What occurs during S of interphase?

Answer 4

Duplication of chromosomes

Question 5

What occurs during G2 of interphase

Answer 5

The cell “double checks” the duplication of chromosomes

Question 6

Cyclin-dependent kinases (____) regulate the stages of the cell cycle.

Answer 6

CDKs

Question 7

Cyclin-dependent kinases (CDKs) require _________ for activity.

Answer 7

Cyclins

Question 8

In addition to cyclin binding, CDKs can be regulated by phosphorylation and ____________ (CKIs).

Answer 8

CDK inhibitory proteins

Question 9

What are the 4 classes of cyclins?

Answer 9

G1

G1/S

S

G2

Question 10

Each cyclin class binds and activates specific _______.

Answer 10

CDKs

Question 11

Cyclin expression _______ and falls at distinct points in the cell cycle.

Answer 11

Rises

Question 12

What stimulates synthesis of G1 cyclins or Cln3 in yeast?

Answer 12

Nutrient accumulation and availability

Cell growth

Question 13

And what stimulates G1 cyclin or cyclin D synthesis in animals?

Answer 13

Nutrient accumulation and availability

Cell growth

Growth factor stimulation

Question 14

While G1 cyclins are synthesized in response to external factors, all other cyclins are synthesized in response to the activity of the _________ CDK. Each active CDK initiates a wave of ___________ that produces the next cyclin.

Answer 14

Preceding

Transcription

Question 15

Just as cyclins must be synthesized, so too must they be degraded. Cyclins are degradaed via ____________ after being targeted by two E3 __________ ________: the _______ complex and the ___________ complex or cyclosome.

Answer 15

Ubiquitin-dependent proteolysis

E3 ubiquitan ligases

SCF complex

Anaphase promoting complex or cyclosome

Question 16

The SCF complex is active throughout the cell cycle, and its targets include G1 cyclins and ___________.

Answer 16

CDK inhibitory proteins (CKIs)

Question 17

The two targets of the SCF complex are…?

Answer 17

G1 cyclins (e.g., Cln3 and cyclin D)

CDK inhibitory proteins (CKIs)

Question 18

The SCF complexes recognizes only ___________ targets.

Answer 18

Phosphorylated

Question 19

Unlike the SCF complex, which is active throughout the cell cycle, the APC/C is only active when phosphorylated by the M phase cyclin/CDK complex at the ______________ to metaphase transition: cyclin ___/CDK ____ in animals.

Answer 19

Cyclin B/CDK1

Question 20

The APC/C complex is only active when phosphorylated around the anaphase to metaphase transition by the M phase cyclin/CDK complex (cyclin B/CDK1). Its targets have specific ______________ box motifs and include the S and M phase cyclins and the proteins that connect sister chromatids or cohesins.

Answer 20

Destruction

The S phase cyclins are cyclin E and cyclin A

The M phase cyclin is cyclin B

Question 21

There are both activating and inhibiting phosphorylations of cyclin-dependent kinases. What protein facilitates activating phosphorylations of cyclin-dependent kinases?

Answer 21

CDK activating kinases (CAKs)

Question 22

CAKs phosphorylate a ___________ residue near the active site of CDKs, which increases CDK activity but is not the _______________ step.

Answer 22

Threonine

Rate-limiting step

Question 23

Inhibitory phosphorylations of CDKs occur at ______ and _____ residues in the ATP-binding site.

Answer 23

Tyrosine

Threonine

Question 24

Wee1 kinases phosphorylate and inhibit which CDK of the cell cycle?

Answer 24

CDK1, the M phase CDK

Question 25

Meanwhile cdc25 phosphatases dephosphorylate and activate _____ or the M phase CDK.

Answer 25

CDK1

(In yeast, CDK1, too)

Question 26

There are four classes are CDK inhibitors or CKIs for each of the four types of CDKs: G1 inhibitors, G1/S inhibitors, ____ inhibitors, and M inhibitors.

Answer 26

S inhibitors

Question 27

G1 inhibitors include ______, which binds CDK 4&6, preventing its ability to bind its cyclin, cyclin D.

Answer 27

INK4 (Inhibitors of kinase 4)

Question 28

INK4 or G1 inhibitors of CDKs are mostly expressed in response to what?

Answer 28

Excessive growth stimulation