Module 2 Control of the Cell Cycle

Question 1

Typical cell cycle in Human cell (time)

Answer 1

G1 - 5 hrs (5-9)
G0 - varied
S - 7 hrs (7-10)
G2 - 3 hrs (3-4 1/2)
M - 1 hr (1/2 - 1)

Question 2

In humans, the frequency of cell turnover ranges from ________ in early embryonic development, to an average of __________ for epithelial cells, and to an entire human lifetime spent in G0 by specialized cells, such as cortical neurons or cardiac muscle cells.

Answer 2

a few hours,
two to five days

Question 3

When fast‐dividing mammalian cells are grown in culture (outside the body under optimal growing conditions), the length of the cycle is about

Answer 3

24 hours

Question 4

In early embryos of fruit flies, the cell cycle is completed in about _____.

Answer 4

eight minutes

Question 5

The timing of events in the cell cycle is controlled by mechanisms that are both ______ and ______ to the cell.

Answer 5

internal and external

Question 6

Both the ______ and _____of cell division are triggered by _______ external to the cell when it is about to begin the replication process.

Answer 6

initiation and inhibition
events

Question 7

An event may be as simple as (4)

Answer 7

• death of a nearby cell
• release of growth-promoting hormones
• crowding of cells (inhibit)
• size of cell

Question 8

example of growth-promoting hormones

Answer 8

human growth hormone (HGH)

Question 9

A lack of HGH can inhibit cell division, resulting in ______, whereas too much HGH can result in _______.

Answer 9

dwarfism
gigantism

Question 10

as a cell grows, it becomes inefficient due to its ______________. The solution to this problem is to divide.

Answer 10

decreasing surface‐to‐volume ratio

Question 11

three main cell cycle checkpoints and their location

Answer 11

• G1 checkpoint - End of G1
• G2 checkpoint - G2/M transition
• M checkpoint - Mitotic phase (end of metaphase)

Question 12

The integrity of the DNA is assessed at the _________. Proper chromosome duplication is assessed at the __________. Attachment of each kinetochore to a spindle fiber is assessed at the ___________.

Answer 12

G1 checkpoint
G2 checkpoint
M checkpoint

Question 13

_________ also called _______(in yeast) determines whether all conditions are favorable for cell division to proceed

Answer 13

G1 checkpoint or restriction point (in yeast)

Question 14

point at which the cell irreversibly commits to the cell division process

Answer 14

G1 checkpoint

Question 15

External influences, such as _________, play a large role in carrying the cell past the G1 checkpoint

Answer 15

growth factors

Question 16

In addition to _______ and ______, there is a check for ___________ at the G1 checkpoint

Answer 16

adequate reserves
cell size
genomic DNA damage

Question 17

If the G1/S checkpoint detects damage, the _______ targets the cell for regulated death (________)

Answer 17

p53 protein
apoptosis

Question 18

In G1 checkpoint, a cell that does not meet all the requirements will not be allowed to progress into the ______. The cell can halt the cycle and attempt to remedy the problematic condition, or the cell can advance into ______ and await further signals when conditions improve

Answer 18

S phase
G0

Question 19

Cells in _________ are not actively preparing to divide. The cell is in a quiescent (inactive) stage that occurs when cells exit the cell cycle.

Answer 19

G0 phase

Question 20

bars entry into the mitotic phase if certain conditions are not met.

Answer 20

G2 checkpoint

Question 21

ensures that that all of the chromosomes have been replicated and that the replicated DNA is not damaged. If the checkpoint mechanisms detect problems with the DNA, the cell cycle is _______, and the cell attempts to either complete DNA replication or repair the damaged DNA

Answer 21

G2 checkpoint
halted

Question 22

• occurs near the end of the metaphase stage of karyokinesis
• it determines whether all the sister chromatids are correctly attached to the spindle microtubules

Answer 22

M checkpoint

Question 23

The M checkpoint is also known as the

Answer 23

spindle attachment checkpoint

Question 24

During M checkpoint, the separation of the sister chromatids during anaphase is an __________, the cycle will not proceed until the kinetochores of each pair of sister chromatids are firmly anchored to at least two spindle fibers arising from opposite poles of the cell.

Answer 24

irreversible step

Question 25

Regulator Molecules of the Cell Cycle are direct regulators of cell cycle transitions

Answer 25

* Cdks, cyclins, and the APC/C (positive regulators) * Rb, p53, and p21 (negative regulators)

Question 26

* either promote progress of the cell to the next phase (positive regulation) or halt the cycle (negative regulation). * may act individually, or they can influence the activity or production of other regulatory proteins

Answer 26

regulatory molecules

Question 27

true or false failure of a single regulator may have almost no effect on the cell cycle, especially if more than one mechanism controls the same event

Answer 27

true

Question 28

True or False the effect of a deficient or non‐functioning regulator can be wide‐ranging and possibly fatal to the cell if multiple processes are affected

Answer 28

true

Question 29

Two groups of proteins, called ________and _______, are responsible for the progress of the cell through the various checkpoints. Cyclins regulate the cell cycle only when they are tightly bound to Cdks.

Answer 29

cyclins cyclin‐dependent kinases (Cdks)

Question 30

protein complex which initiates the mitotic phase of the cell cycle

Answer 30

Mitosis‐promoting factor

Question 31

Mitosis‐promoting factor is made of two proteins:

Answer 31

Cyclin B and CDC2

Question 32

one that oscillates in quantity during the cell cycle

Answer 32

Cyclin B

Question 33

- constant quantity - a kinase - encoded by the _____ gene

Answer 33

CDC2 by *cdc2* gene

Question 34

True or False CDC2 kinase is still functional when it is not combined with cyclin which is referred as cyclin‐dependent kinase (CDK)

Answer 34

False CDC2 kinase is only functional when it is combined with cyclin which is referred as cyclin‐dependent kinase (CDK)

Question 35

permits the separation of the sister chromatids at the start of anaphase

Answer 35

anaphase‐promoting complex (APC) or cyclosome

Question 36

degrades the Cyclin B protein of MPF

Answer 36

anaphase‐promoting complex (APC) or cyclosome

Question 37

what phase does MPF activity starts

Answer 37

G2

Question 38

what phase does MPF activity starts and ends

Answer 38

G2 - M phase check graph!

Question 39

Remember that in positive regulation, __________ cause the cycle to progress

Answer 39

active molecules

Question 40

halt the cell cycle

Answer 40

Negative regulators

Question 41

best understood negative regulatory molecules

Answer 41

Rb (Retinoblastoma proteins) p53 p21

Question 42

a group of tumor-suppressor proteins common in many cells

Answer 42

retinoblastoma protein

Question 43

The 53 and 21 designations refer to the ___________ of the proteins (p) in ________

Answer 43

functional molecular masses kilodaltons

Question 44

All three of these regulatory proteins were discovered to be ______ or ___________ in cells that had begun to replicate uncontrollably (became ___________). In each case, the main cause of the unchecked progress through the cell cycle was a faulty copy of the regulatory protein.

Answer 44

damaged or non‐functional cancerous

Question 45

Cancer cells can become tumors ___ remain clustered and can be removed ____ are able to ___ or break away and form new tumors ____ are substances that promote cancer

Answer 45

Benign tumors Malignant tumors Metastasize Carcinogens

Question 46

Rb, p53, and p21 act primarily at the _____ checkpoint

Answer 46

G1 checkpoint

Question 47

is a multi‐functional protein that has a major impact on the commitment of a cell to division because it acts when there is damaged DNA in cells that are undergoing the preparatory processes during G1. If damaged DNA is detected, it halts the cell cycle and recruits enzymes to repair the DNA

Answer 47

p53

Question 48

If the DNA cannot be repaired, ______ can trigger ______, or cell suicide, to prevent the duplication of damaged chromosomes

Answer 48

p53 apoptosis

Question 49

As p53 levels rise, the production of ____ is triggered

Answer 49

p21

Question 50

enforces the halt in the cycle dictated by p53 **by binding to and inhibiting the activity of the Cdk/cyclin complexes**

Answer 50

p21

Question 51

As a cell is exposed to more stress, higher levels of p53 and p21 accumulate, making it less likely that the cell will move into the

Answer 51

S phase

Question 52

* exerts its regulatory influence on other positive regulator proteins. * monitors cell size

Answer 52

Rb

Question 53

In the active, dephosphorylated state, Rb binds to proteins called _____________, most commonly, _____.

Answer 53

transcriptions factors, E2F

Question 54

"turn on” specific genes to produce certain proteins

Answer 54

transcriptions factors

Question 55

When Rb is bound to ______, production of proteins necessary for the G1/S transition is blocked. As the cell increases in size, Rb is slowly ________until it becomes inactivated.

Answer 55

E2F phosphorylated

Question 56

As Rb releases E2F, it _____ the gene that produces the transition protein, and this particular block is removed.

Answer 56

"turned on"

Question 57

For the cell to move, past each of the checkpoints, all positive regulators must be ______ and all negative regulators must be ______

Answer 57

turned on turned off

Question 58

Rb and other proteins that negative regulate the cell cycle are sometimes called ______

Answer 58

tumor suppressors

Question 59

Apoptosis is also known as ____ It occurs in normal development when cells are temporarily required for a maturation process. It also occurs in genetically damaged cells and older cells that rare no longer necessary. An example being (2)

Answer 59

Programmed Cell Death Embryonic Development Metamorphosis

Question 60

A well-known example of apoptosis is in the animal ____ It is signaled by the ____ which causes the animal to digest their tail cells, reabsorbing and recycling the digestion products into new structures

Answer 60

Frog (frog metamorphosis) Thyroid hormone

Question 61

Cells that die from an unexpected injury undergo ____ which is an accidental death.

Answer 61

Necrosis

Question 62

In nectrotic cells, * the ____ does not shrink or fragment * nuclear morphology changes * ____ form but fuse (enlarge) * no _______ in blebs * the ____ bursts to release the cell contents into the extracellular environment * organelles are ______

Answer 62

nucleus Blebs organelles cell membrane non-functional

Question 63

In apoptosis, * Nucleus ____ * the blebs turn into ____ * ______ spread to blebs * _______ are not released into the extracellular environment * organelles still _____

Answer 63

fragment apoptotic bodies organelles cell contents functional

Question 64

Cell Division Rate 1. skin cell 2. RBC 3. liver cell 4. intestine (internal lining) 5. intestine (muscle and other tissues)

Answer 64

1. skin cell - 2 weeks 2. RBC - 4 months 3. liver cell - 300-500 days 4. intestine (internal lining) - 4-5 days 5. intestine (muscle and other tissues) - 16 years

Question 65

P21 inhibits CDK __, ___, ___, & ___

Answer 65

CDK 2, 3 ,4, & 6

Question 66

Environment determines what form of reproduction is most advantageous. * _______ is an advantage in consistently favorable conditions. * _______ is an advantage in changing conditions.

Answer 66

Asexual reproduction Sexual reproduction

Question 67

Asexual reproduction (3)

Answer 67

* Budding * Fragmentation * Vegetative reproduction

Question 68

forms a new organism from a small projection growing on the surface of the parent.

Answer 68

budding

Question 69

is the splitting of the parent into pieces that each grow into a new organism.

Answer 69

fragmentation

Question 70

forms a new plant from the modification of a stem or underground structure on the parent plant

Answer 70

Vegetative reproduction

Question 71

________ cells perform specific functions. Cells develop into their mature forms through the process of ____________. Cells differ because different combinations of _______ are expressed. A cell’s _____ in an embryo helps determine how it will differentiate

Answer 71

Specialized cells cell differentiation genes location

Question 72

- are unique body cells - have the ability to: * divide and renew themselves * remain undifferentiated in form * develop into a variety of specialized cell types

Answer 72

stem cells

Question 73

Stem cells are classified into three types

Answer 73

totipotent pluripotent multipotent

Question 74

growing into any other cell type

Answer 74

totipotent

Question 75

growing into any cell type but a totipotent cell (almost any cell)

Answer 75

pluripotent

Question 76

growing into cells of a closely related cell family

Answer 76

multipotent

Question 77

Stem cells come from _____ and ________

Answer 77

adults and embryos

Question 78

* can be hard to isolate and grow * use of these may prevent transplant rejection.

Answer 78

Adult stem cells

Question 79

* are pluripotent and can be grown indefinitely in culture * use of this raises ethical issues

Answer 79

embryonic stem cells

Question 80

The use of ______ offers many currently realized and potential benefits. * are used to treat leukemia and lymphoma. * may cure disease or replace damaged organs. * may revolutionize the drug development process.

Answer 80

stem cells