EXAM 4 LEC 18

Question 1

M phase

Answer 1

mitosis and cytokinesis

Question 2

interphase

Answer 2

G1 phase, S phase, and G2 phase

Question 3

retinoblastoma protein

Answer 3

inhibitor of cell proliferation genes

Question 4

cyclin CdK complexes

Answer 4

activators of the cell cycle

Question 5

p53 protein activation of p21 gene expression

Answer 5

inhibitor of CdK

Question 6

G1 phase

Answer 6

damaged DNA and internal/external environment

Question 7

S phase

Answer 7

damaged or partial replication

S-cyclin-CdK

Question 8

G2 phase

Answer 8

damaged or partial replication

M-cyclin-CdK

Question 9

M phase

Answer 9

chromosome attachment

anaphase promoting complex (APC)

Question 10

mitogen activation of cell cycle (G1)

Answer 10

Rb protein binds transcriptional activators and prevents transcription of cell proliferation genes
mitogen binds to a receptor
activated MAP kinase signal transduction
activates G1-CdK and G1/S-CdK complexes
phosphorylation of Rb protein releases the transcriptional activators

Question 11

mitogen

Answer 11

a local mediator

Question 12

mitosis

Answer 12

nuclear division

Question 13

cytokinesis

Answer 13

cytoplasmic division

Question 14

activation of cyclin-dependent protein kinases (CdKs)

Answer 14

specific cyclin interacts with specific CdK but protein complex nonfunctional
Wee1 phosphorylates CdK in the protein complex and inactivates the complex
Cdc25 removes the inhibitory phosphates (dephosphorylate) to activate the CdK complex

Question 15

Wee1

Answer 15

protein kinase

Question 16

Cdc25

Answer 16

protein phosphate

Question 17

what does an active CdK complex require

Answer 17

cyclin plus CdK with removal of the inhibitory phosphate

Question 18

cyclin-dependent kinases are

Answer 18

always present in actively dividing cells

Question 19

abundance of M-Cdk

Answer 19

remains relatively constant in actively dividing cells during the cell cycle

Question 20

activity of Cdk

Answer 20

varies because it requires an active cyclin-Cdk complex

Question 21

variation in abundance of a specific Cdk

Answer 21

modulates activity during the cell cycle

Question 22

what causes delayed and amplified Cdk activity

Answer 22

initial inhibition of cyclin-Cdk activity and induction of Cdk activity by feedback positive removal of inhibition

Question 23

what activates M-Cdk

Answer 23

Cdc25 phosphatase that removes the inhibitory phosphates

Question 24

function of activated M-Cdk

Answer 24

phosphorylates Cdc35 phosphatase

Cdc25 removes more inhibitory phosphates on M-Cdk

Question 25

ubiquitylated cyclin

Answer 25

sent to proteasome for degradation

Question 26

p53

Answer 26

transcription activator
high turnover rate of inactivated form
DNA damage signal activates protein kinases that phosphorylate p53
activated p53 is a stable transcription activator
cell cycle is stopped by activated p53

Question 27

p21

Answer 27

gene expression induced by activated p53

encodes a Cdk inhibitor protein that specifically binds to G1/S-Cdk

Question 28

temperature sensitive cell cycle mutants

Answer 28

yeast

have mutations that cause phenotypes only when there is a change in temperature, otherwise they are silent mutations

Question 29

use of temperature sensitive mutants

Answer 29

when the mutated gene is critical to the organism that the absence is lethal. the organism can be maintained at the temperature where the mutation is silent and the effect of gene loss can be monitored at the temperature that causes the lethal phenotype