Cell Division

Question 1

Basic cell cycle outline

Answer 1

Question 2

Graph of Cyclin Concentration Over Time

Answer 2

Question 3

Cyclin-CDK / Cell Cycle Overlay

Answer 3

Question 4

Cyclin / CDK model including Cyclin C-CDK3 and Cyclin H-CDK7

Answer 4

Question 5

Role of Cyclin C-CDK3

Answer 5

Drives re-entry from G₀

Question 6

Role of Cyclin H-CDK7-MAT1

Answer 6

Enables Cyclin B-CDK1 activity

Question 7

Role of Cyclin D-CDK4/6

Answer 7

Activated during G1 phase of the cell cycle. The level of cyclin D-CDK activity is important in helping the cell decide whether or not to divide. The higher the level of activity, the more likely it is to divide.

Question 8

Role of Cyclin E-CDK2

Question 9

Role of Cyclin A-CDK2

Question 10

Role of Cyclin A-CDK1

Question 11

Role of Cyclin B-CDK1

Question 12

Regulation of Cyclin-CDKs

Answer 12

Question 13

Three mechanisms of CDK regulation

Answer 13

1. Synthesis and degradation (E3 ubiquitination) of cyclin and CDK subunits
2. Regulation by other protein kinases and phosphatases
3. Inhibitors of CDK activity (INKs)

Question 14

Coordination of Growth and Cell Cycle Progression

Answer 14

Question 15

Relevance of integrin signaling to cell division

Answer 15

Question 16

Rb-E2F regulation

Answer 16

Question 17

The INKs

Answer 17

Question 18

Prokaryotic vs Eukaryotic DNA replication

Answer 18

Question 19

Segregation of Origin Assembly and DNA Replication

Answer 19

Question 20

Prereplication Complex Regulation

Answer 20

Question 21

The prereplication complex is activated to begin transcription by. . .

Answer 21

E or A Cyclins and associated CDKs

Question 22

Initiation of Replication

Answer 22

Question 23

Rpa

Answer 23

Binds to ssDNA during replication to prevent it from reannealing.

Question 24

Regulation of S phase replication

Answer 24

Question 25

Pol δ

Answer 25

DNA Polymerase utilized in replication

Question 26

PCNA

Answer 26

Keeps Pol δ attached to the DNA during replication

Question 27

What keeps initiation factors from binding to the new strands of DNA that are being produced during replication?

Answer 27

Phosphorylation by high levels of Cyclin E/Cyclin A-CDK complexes

Question 28

Sustained CDK activity during S phase and G2 is essential to . . .

Answer 28

1. Promote completion of DNA replication 2. Prevent re-initaition and re-replication of replicated DNA

Question 29

Fundamental logic of the Cyclin-CDK solution to the problem of segregating replication and initiation

Answer 29

Question 30

Mitosis imaged by fluorescence microscopy

Answer 30

Question 31

Location of the G2-M Checkpoint

Answer 31

Question 32

Wee1

Answer 32

Kinase which is activated by signaling from active DNA replication forks. Phosphorylates Cyclin B-CDK1 complexes on two N-terminal residues (Thr14, Tyr 15) which inhibits Cyclin B-CDK1 activity. This prevents mitosis from starting until DNA replication is complete.

Question 33

Cdc25

Answer 33

Phosphatase which is activated when replication forks disappear (replication is over) Removes the inhibitory Thr14 and Tyr15 phosphate groups on Cyclin B-CDK1, which were placed by Wee1, and allows the cell to enter mitosis.

Question 34

How Cyclin B-CDK1 breaks down the nuclear lamina

Answer 34

Question 35

Condensation of DNA for mitosis

Answer 35

This condensation is mediated by Cyclin B-CDK1

Question 36

Centromeres and Kinetochores

Answer 36

Question 37

Cohesin

Answer 37

Question 38

Cohesins are cut as part of the _____ to _____ transition.

Answer 38

Cohesins are cut as part of the **metaphase** to **anaphase** transition.

Question 39

During mitosis, the Golgi and ER. . .

Answer 39

. . .become fragmented into vesicles and are passively distributed to the two daughter cells.

Question 40

Bipolar attachment

Answer 40

Each sister chromatid in a single chromosome is attached to microtubules coming from one end of the mitotic spindle

Question 41

Metaphase-Anaphase Checkpoint Location

Answer 41

Question 42

Sequences Required for Cyclin B degradation

Answer 42

Question 43

Degron

Answer 43

Sequence that targets the protein for regulated degradation (not necessarily constitutive)

Question 44

The E3 for Cyclin B is. . .

Answer 44

APC/C aka Anaphase promoting complex / cyclosome (Not to be confused with adenomatous polyposis coli, the tumor suppressor gene product, or antigen presenting cell)

Question 45

Role of Cdc20 in Cyclin B regulation

Answer 45

Cdc20 is the receptor which associates with the APC/C complex in order to target Cyclin B for degradation. Cdc20 recognizes only phosphorylated Cyclin B, and so it will not degrade Cyclin B prior to the metaphase-anaphase transition.

Question 46

Securin

Answer 46

Inhibits separase until APC/C is activated. It senses APC/C activation because. . . it is an APC/C target! This is how Cyclin B-CDK1 destruction is tied to the beginning of anaphase: Once APC/C is active, all of the sudden Cyclin B-CDK1 and securin are both gone.

Question 47

The Separase-Securin System

Answer 47

Question 48

\_\_\_\_\_ is what is sensed by the spindle checkpoint

Answer 48

**Tension** is what is sensed by the spindle checkpoint If a chromosome is not under tension, it means is must not be attached properly, and thus the spindle checkpoint is activated.

Question 49

Drop in CDK activity at the end of mitosis and cytokinesis leads to. . .

Answer 49

. . . inactivating dephosphorylation of the proteins that form pre-replication complexes. These will be reactivated after the G₁/S transition.

Question 50

We can boil down the logic of the cell cycle to an oscillation between. . .

Answer 50

We can boil down the logic of the cell cycle to an oscillation between **CDK activity and APC/C activity**