LC 40

Question 1

Checkpoints of mitosis

Answer 1

There are three points where the cell cycle is regulated: G1/S, G2/M and M checkpoints

Question 2

How does a cell decide when to divide?

Answer 2

growth signals
cell size
DNA damage

Question 3

CDK

Answer 3

cyclin dependent kinases integrate multiple signals to determine whether to proceed through a checkpoint

Question 4

Growth signals

Answer 4

Growth signals are an important signal for progressing through the G1/S checkpoint and starting the cell cycle

Question 5

cyclins

Answer 5

cyclins are the time-keepers of the cell cycle and insure each step happens in the correct sequence

Question 6

G1/S checkpoint and protein involved

Answer 6

growth signals, cell size, DNA damage

pRb, p53, E2F, AKT

Question 7

Regulation

Answer 7

Describe how the cell cycle is regulated

Question 8

G2/M checkpoint

Answer 8

Checks for: DNA replication, DNA damage, cell size

Question 9

M checkpoint

Answer 9

checks for spindle attachment and chromosome distribution

Question 10

p53

Answer 10

critical control component of cell cycle regulation

Question 11

E2F

Answer 11

Travels to the nucleus and promotes transcription of DNA

Question 12

pRb

Answer 12

critical control component of cell cycle regulation. Prevents E2F from being activated until we really want to go into S phase

Question 13

AKT

Answer 13

Also called protein kinase B, has two potential internal signals. Kinase that inhibits cell cycle arrest (phosphorolates CDK) and inhibits apoptosis

Question 14

Mis-regulation

Answer 14

describe

Question 15

Retinoblastoma Protein

Answer 15

pRB - is commonly mutated in tumors

Question 16

pRB and cancer

Answer 16

mutations is pRB turn the G1/S checkpoint permanently on and can cause runaway cell division

Question 17

G0 phase

Answer 17

quiescence

Question 18

G1 phase

Answer 18

growing stage, 1 set of chromosomes

Question 19

S phase

Answer 19

Synthesis, DNA replication

Question 20

G2 phase

Answer 20

Growing stage, 2 sets of chromosomes

Question 21

M phase

Answer 21

Mitosis, cell division

Question 22

Interphase

Answer 22

G1, S, G2 - this is the stage that non-dividing cells are in

Question 23

Prophase

Answer 23

Chromosomes condense and centrosomes duplicate

Question 24

prometaphase

Answer 24

centrosomes go to opposite sides of the cell and nuclear envelop disassembles

Question 25

metaphase

Answer 25

Chromosomes are on the metaphase plate - important checkpoint for division

Question 26

anaphase

Answer 26

Daughter chromosomes are pulled apart

Question 27

telophase

Answer 27

Chromatids on opposite sides and nuclear envelope reforms

Question 28

cytokinesis

Answer 28

Cells are split by contractile ring and microtubules form interphase array - this step does not always occur for example multi-nucleated cells

Question 29

Cell cycle

Answer 29

G1, S, G2, M G0

Question 30

3 signals of CDK to activate and move through a checkpoint

Answer 30

1) remove a phosphate
2) adds a phosphate to other spot (kinase)
3) bind cyclin

Question 31

Purpose of growth signals

Answer 31

the cells requires growth signals to divide.

Question 32

Examples of growth signals

Answer 32

EGF, IGF-1, PDGF, EPO

Question 33

EGF

Answer 33

epithelial growth factor

Question 34

IGF-1

Answer 34

insulin like growth factor

Question 35

PDGF

Answer 35

platelet derived growth factor

Question 36

EPO

Answer 36

erythropoietin

Question 37

Estrogen purpose as a growth signal

Answer 37

signal for female reproductive cell growth

Question 38

Testosterone purpose as a growth signal

Answer 38

signal for male reproductive cell growth

Question 39

EGF pathway (G1 cyclin)

Answer 39

EGF–>TK receptor (EGFR)–>SOS–>exchanges GDP for GTP to activate Ras–> MAPK cascade –>transcription factor –>Jun, Myc, Fos–> can result in many proteins but G1 cyclin, E2F and G1-CDK are just a few examples–>progression through G1/S checkpoint

Question 40

EGF pathway (Akt)

Answer 40

EGF–>TK receptor (EGFR) dimerization and phosphorylation–> P13-Kinase recruited–>PIP2–>PIP3–>phosphorylation cascade–>PDPK1–>Akt (PKB) –> apoptosis and cell cycle arrest are stopped

Question 41

Wnt pathway

Answer 41

inside the cell APC, Axin and GSK3 make a complex—>complex ubiquitinates catenin B so it is now targeted for degradation–> outside the cell Wnt binds to LRP/Frizzled receptor–> this complex recruits and phosphorylates disheveled which recruits Axin and GSK3–>this prevents complex assembly–>Catenin B can now be transported to the nucleus where it activates LEF and TCF transcription factors–>these transcribe cell cycle related proteins

Question 42

G1 phase cyclin

Answer 42

Cyclin D

Question 43

S phase cyclin

Answer 43

cyclin E

Question 44

G2 phase cyclin

Answer 44

cyclin A

Question 45

M phase cyclin

Answer 45

cyclin B

Question 46

Mitosis promoting factor activity

Answer 46

CDK-cyclin B complex

Question 47

Cyclins always effect…

Answer 47

CDKs

Question 48

Activated cyclin CDK complexes trigger the next step and _______ the current cyclin

Answer 48

degrades

Question 49

cyclins act like a cell cycle ______ and prevent steps from running in ______

Answer 49

clock, reverse

Question 50

G1/S checkpoint pathway

Answer 50

Growth factors–>CDK1 phosphorylates Rb protein–>Rb protein releases E2F (transcription factor)–>E2F goes to nucleus and transcribes DNA replication genes

Question 51

What pathway is in place to prevent G1/S pathway from moving forward if DNA is damaged?

Answer 51

ATM protein is activated–>ATM phosphorylates p53–>activated p53–>transcription factor for p21–>p21 inhibits CDK1

Question 52

pRB and cancer

Answer 52

mutations in pRB turn the G1/S checkpoint permanently on and cause runaway cell division because E2F cannot be bound and is not regulated so it continues to work at high amounts.