Chapter 14

Question 1

What happens during G1 phase?

Answer 1

cells grow and carries out normal metabolism; organelles duplicate

Question 2

What happens during S phase?

Answer 2

DNA replication and chromosome duplication

Question 3

What happens during G2 phase?

Answer 3

Cell grows and prepares for mitosis

Question 4

What is M phase and how long does it last?

Answer 4

includes process of mitosis and cytokinesis; mitosis lasts about an hour

Question 5

What is interphase?

Answer 5

constitutes the majority of the cell cycle and lasts longer than the M phase; it may extend for days, weeks, or longer

Question 6

What is maturation promoting factor (MPF) and what are its characteristics?

Answer 6

1) Protein kinase that triggers the entry into M phase
2) Consists of a kinase and a regulatory subunit, cyclin
3) Increased cyclin conc. activates the kinase

Question 7

What is the role of protein kinases in the yeast cell model?

Answer 7

1) Cyclin-dependent kinases (Cdks)
2) For cells to pass through, Cdks must be transiently activated by specific cyclins.
3) Activated Cdk phosphorylates proteins for transition

Question 8

Where does cell cycle regulation occur in fission yeast?

Answer 8

Control is primarily at two points: START (late G1) and the G2-M transition

Question 9

What does progression through the fission yeast cell cycle require?

Answer 9

Phosphorylation and dephospho rylation of critical cdc2 residues

Question 10

What are the steps in Cdk activation?

Answer 10

1) Cdc-activating kinase (CAK) phosphorylates both a threonine and a tyrosine on the Cdk subunit. Wee 1 and Cyclin are added.
2) The doubly phosphorylated Cdc-cyclin is inactive
3) A phosphatase (cdc25) removes one phosphate
4) Single phosphorylated cyclin is active, driving cell to mitosis

Question 11

What are CAK and cdc25 activated by?

Answer 11

other kinases and phosphatases

Question 12

What protein controls cell cycle progression?

Answer 12

Sic1

Question 13

What are some characteristics of controlled proteolysis?

Answer 13

1) Occurs via the ubiquitin proteasome pathway
2) Two classes of multisubunit complexes function as ubiquitin ligases
3) Destruction of the mitotic cyclins allow a cell to exit mitosis and enter a new cell cycle.

Question 14

What is the SCF pathway?

Answer 14

SCF ubiquitin ligase enables the entry into S phase by promoting degradation of the S-phase cyclin-dependent kinase inhibitor

Question 15

How does Cyclin B1 enter the nucleus?

Answer 15

Serine phosphorylation of NES sequence allows it to enter the nucleus

Question 16

What happens if nuclear accumulation of cyclin is blocked?

Answer 16

Cells fail to initiate mitosis

Question 17

What is the only Cdk required to drive a mammalian cell through the cell cycle?

Answer 17

Cdk1

Question 18

Lack of which proteins would be lethal?

Answer 18

Cdk1, CycB1, CycA1

Question 19

What are Cyclin D’s paired with?

Answer 19

Cdk4 and Cdk6

Question 20

What is Cyclin E paired with?

Answer 20

Cdk2

Question 21

What is Cyclin A paired with?

Answer 21

Cdk2

Question 22

What are Cyclin B/A paired with?

Answer 22

Cdk1

Question 23

pRB phosphorylation leads to the expression of:

Answer 23

CycF, CycA, and cdk1

Question 24

What are sensors, transmitters and effectors?

Answer 24

1) sensors- detect chromosomal abnormalities
2) transmitters- signal the information
3) effectors- inhibit cell cycle machinery

Question 25

What are two pathways that stop the cell the cycle progress?

Answer 25

1) Chki inhibits Cdc25 when DNA is damaged | 2) The protein p21 inhibits the G1 Cdk when DNA is damaged

Question 26

What is the role of p27?

Answer 26

Progression through the S phase is inhibited by the action of p27, which is a Cdk inhibitor

Question 27

How does p27 inhibit Cdk?

Answer 27

Forms a trimeric complex with CycA and Cdk2, preventing their activity

Question 28

What is the result of the elimination of p27?

Answer 28

excess cell proliferation and organ growth in p27 knockout

Question 29

What happens during prophase?

Answer 29

Duplicated chromosomes are prepared for segregation and the mitotic machinery is assembled

Question 30

When does chromosome compaction occur?

Answer 30

early prophase

Question 31

What is the protein responsible for compaction?

Answer 31

condensin

Question 32

What is the difference between condensin and cohesin? How are they similar?

Answer 32

1) Condensing helps compaction of intramolecular DNA 2) Cohesin helps connect sister chromatids (inter) 3) Both contain SMC proteins

Question 33

What happens during metaphase?

Answer 33

chromosomes are aligned at the spindle equator on the metaphase plate

Question 34

What is the function of astral microtubules?

Answer 34

radiate from the centrosome to the region outside the body of the spindle

Question 35

What is the function of chromosomal microtubules?

Answer 35

move chromosomes to the poles

Question 36

What is the function of polar microtubules?

Answer 36

maintain the integrity of the spindle

Question 37

What happens during anaphase?

Answer 37

begins when sister chromatids split and move apart

Question 38

What is the role of proteolysis in progression through mitosis?

Answer 38

1) the anaphase promoting complex (APC) is activated at the metaphase/ anaphase transition. 2) An APC subunit marks an anaphase inhibitor (securin) for destruction 3) Securin destruction activates separate, which cleaves cohesin

Question 39

What are SCF and APC?

Answer 39

Multisubunit complexes that ubiquitinate substrates, leading to their destruction by proteasomes

Question 40

What is an example of a spindle assembly checkpoint?

Answer 40

mad2-cdc20 association regulates cdc20-APC formation.

Question 41

What is the contractile ring theory about cytokinesis?

Answer 41

suggested that a thin band of actin and myosin filaments generates the force to cleave the cell

Question 42

How is the site of filament assembly determined?

Answer 42

a signal coming form the spindle poles