18.1 The Eukaryotic Cell Cycle

Question 1

4 main steps in the division cycle

Answer 1

1. cell growth - maintains size of daughter cells
2. DNA replication
3. distribution of the duplicated chromosomes to daughter cells
4. cell division

Question 2

in the cell cycle, () is the most dramatic phase, yet most of the time the cell remains in interphase where the cell steadily grows (may reach up to double in size)

Answer 2

cell division (mitosis)

Question 3

timing of DNA synthesis divides cell cycle into 4 main phases

Answer 3

1. M phase
2. G1 (gap 1)
3. S phase (synthesis)
4. G2 (gap 2)

Question 4

cell cycle phase with mitosis (nuclear division); usually ends with cytokinesis

Answer 4

M phase

Question 5

cell cycle phase that is the interval between mitosis and DNA replication; the cell is metabolically active and growing and there is no DNA replication

Answer 5

G1

Question 6

cell cycle phase with DNA replication

Answer 6

S phase

Question 7

cell cycle phase with synthesis of proteins in preparation for mitosis

Answer 7

G2

Question 8

some cells remain in a prolonged resting state called () and only divide in response to the appropriate extracellular signals (e.g. skin fibroblasts in response to wounds)

Answer 8

G0

Question 9

cells in G0 may reenter the cell cycle in response to ()

Answer 9

appropriate extracellular signals

Question 10

DNA content at different stages of the cell cycle can be measured through (1) detected by a (2) or (3)

Answer 10

1. fluorescence intensity
2. flow cytometer
3. fluorescence-activated cell sorter

Question 11

DNA content in animal cells in G1

Answer 11

diploid

Question 12

cells in S phase have DNA content ranging from (..)

Answer 12

2n to 4n

Question 13

in G2, DNA content remains at (1) and decreases to () after cytokinesis

Answer 13

1. 4n
2. 2n

Question 14

() is the most fundamental characteristic of cells → must be carefully regulated and coordinated

Answer 14

self-reproduction by cell division

Question 15

extracellular signals that regulate animal cell cycle proliferation

Answer 15

growth factors

Question 16

major cell cycle regulatory point; controls progression from G1 to S

Answer 16

START

Question 17

START was first identified using studies involving ()

Answer 17

budding yeasts (Saccharomyces cerevisiae)

Question 18

if requirements aren’t met, cells cannot progress past START and thus enter ()

Answer 18

G0 (cell cycle progress is arrested)

Question 19

give examples of factors that regulate passage through START

Answer 19

• internal and external signals (availability of nutrients, cell size)
• presence of mating factors

Question 20

regulatory point in G1 of animal cells; analogous to START in yeast cells

Answer 20

restriction point

Question 21

passage through G1 restriction point is primarily regulated by (), which signal the cell’s permittance to proceed to synthesis and the rest of the cell cycle

Answer 21

extracellular growth factors

Question 22

skin fibroblasts remain in G0 in adulthood until stimulated by () to proliferate and repair wound damange

Answer 22

platelet-derived growth factor (PDGF)

Question 23

in fission yeast (Schizosaccharomyces pombe) cell cycle is controlled by transition from ()

Answer 23

G2 to M

Question 24

the () of a fission yeast cell indicates its position in the cell cycle

Answer 24

length

Question 25

vertebrate oocyte proliferation is signaled by ()

Answer 25

hormonal stimulation

Question 26

without hormonal stimulation, vertebrate oocytes remain arrested in ()

Answer 26

G2

Question 27

regulate the cell cycle by coordinating the different cell cycle phases

Answer 27

cell cycle checkpoints

Question 28

cell cycle checkpoints prevent entry into the next phase of the cell cycle until ()

Answer 28

the events of the preceding phase have been completed

Question 29

ensure that damaged DNA is not replicated (in G1 → S) and passed on to daughter cells (G2 → M)

Answer 29

DNA damage checkpoints

Question 30

DNA damage checkpoints coordinate cell cycle progression with the ()

Answer 30

completion of DNA replication or repair (e.g. checkpoints in G1, G2)

Question 31

() continuously monitors DNA integrity as well as acts as a quality control monitor to promote DNA repair

Answer 31

S phase checkpoint

Question 32

stops mitosis at metaphase if chromosomes are not properly aligned on the spindle

Answer 32

spindle assembly checkpoint

Question 33

spindle assembly checkpoint ensures that a () is distributed accurately to daughter cells

Answer 33

complete set of chromosomes