BI203 Lecture 23: The Cell Cycle - Stages of Cell Cycle/Checkpoints (Slides 1 - 19)

Question 1

The 3 signaling pathways which can regulate cell proliferation:

Answer 1

cAMP pathway, PI 3-kinase/Akt pathway, ERK MAP Kinase pathway

Question 2

In eukaryotic cells, progression through the cell cycle is controlled by ___ ___ that have been conserved from yeasts to mammals.

Defects in cell cycle regulation are a common cause of the abnormal proliferation of ___ cells.

Answer 2

protein kinases, cancer

Question 3

Bacteria do ___ have a cell cycle. They instead replicate DNA and divide about once every 20 min.

Answer 3

NOT

Question 4

The Eukaryotic cell cycle has ___ phases.

Answer 4

4

Question 5

The 4 phases of the Eukaryotic Cell Cycle:

Answer 5

M, G1, S, G2

Question 6

___ phase - Nuclear division, usually ending with cell division (cytokinesis).

Answer 6

M (mitosis) phase

Question 7

___ phase - Interval between mitosis and DNA replication. The cell is metabolically active and growing.

Answer 7

G1 (gap 1) phase

Question 8

___ phase - DNA replication takes place.

Answer 8

S (synthesis) phase

Question 9

___ phase - Cell growth continues; proteins are synthesized in preparation for mitosis.

Answer 9

G2 (gap 2) phase

Question 10

___ - Period between mitoses, divided into G1, S, and G2.

Answer 10

Interphase

Question 11

A major control point called ___ controls progression from G1 to S, first defined in yeast cells.

Once a yeast cell pass ___, they are committed to entering S phase and undergoing one division cycle.

Answer 11

START

Question 12

Passage through START is highly regulated by external signals, such as ___ availability and cell ___.

If there is a shortage of nutrients, yeast cells can arrest the cycle at START and enter a resting phase.

In order to maintain constant size, yeast cells must reach a minimum ___ to pass START.

Answer 12

nutrient, size, size

Question 13

In most animal cells, the ___ ___ in late G1 functions like START. Once it has passed the ___ ___, the animal cell is committed to proceed through S phase and the rest of the cell cycle.

Answer 13

restriction point

Question 14

If appropriate growth factors are not present in G1, progression stops at the restriction point and animal cells enter a resting stage called ___.

Answer 14

G0

Question 15

Skin fibroblasts, for example, are arrested in ___ until stimulated by platelet-derived growth factor to proliferate and repair wound damage.

Answer 15

G0

Question 16

Coordination of the cell cycle phases is dependent on a series of ___ ___ ___. They prevent entry into the next phase until events of the preceding phase have been completed.

Answer 16

cell cycle checkpoints

Question 17

___ ___ ___ ensure that damaged DNA is not replicated and passed on to daughter cells. The cell cycle is then arrested until DNA is repaired or replicated.

Answer 17

DNA damage checkpoints

Question 18

The ___ ___ ___ ensures that all chromosomes are

aligned on the metaphase plate before cell divides.

Answer 18

spindle assembly checkpoint

Question 19

The spindle assembly checkpoint stops mitosis at ___ if chromosomes are not properly aligned on the spindle.

Answer 19

metaphase

Question 20

___ ___ (Cdk’s) and ___ together control progression through all phases of the cell cycle.

Answer 20

cyclin-dependent kinases (Cdk’s), cyclins

Question 21

___ = Family of kinases that promote cell cycle progression when active.

Answer 21

Cdk’s

Question 22

___ = Family of regulatory subunits required for catalytic activity of Cdk’s.

Answer 22

cyclins

Question 23

The first identified Cdk/cyclin = ___/___ ___, aka ___

Answer 23

Cdk1/cyclin B, aka MPF

Question 24

MPF was discovered during studies of frog egg (= big cells) ___.

Answer 24

maturation

Question 25

Studies of frog oocytes, which are arrested in G2 until hormonal stimulation triggers entry into M phase.

In 1971, researchers found that oocytes could be induced to enter M phase by microinjection of cytoplasm from oocytes that had been hormonally stimulated.

The responsible cytoplasmic factor from G2 cells was called ___ ___ ___ (MPF).

Answer 25

maturation promoting factor (MPF)

Question 26

___ = Kinase whose activity induces entry into meiosis.

Answer 26

Cdk1

Question 27

___ ___ = Regulatory protein required for Cdk1 kinase activity.

Answer 27

Cyclin B

Question 28

MPF activity is required in ___ ___ ___ for progression from G2 to M.

Answer 28

all eukaryotic cells

Question 29

Cells synthesize Cyclin B throughout the cell cycle, during which it accumulates to “threshold levels” at the end of ___. This stimulates MPF activity.

Answer 29

G2

Question 30

Cyclin B can be ___ and ___, causing inactivation of Cdk1 and an exit from M phase.

Answer 30

ubiquitylated, degraded

Question 31

Ubiquitylation of cyclin B is mediated by a ubiquitin ligase: ___/___

Answer 31

APC/C

Question 32

Once any cyclin has induced its necessary progression in the cell cycle, it is then ___ by a ___.

Answer 32

degraded, proteasome

Question 33

MPF activity can also be regulated by ___. The Cdk1/cyclin B complex is ___ by a kinase, deactivating the complex.

Answer 33

phosphorylation, phosphorylated

Question 34

Inhibitory proteins of Cdk’s: ___ ___ (CKIs)

There are 2 families in animal cells: Ink4 and Cip/Kip

Answer 34

Cdk inhibitors (CKIs)