Chapter 18

Question 1

anaphase

Answer 1

Stage of mitosis during which the two sets of chromosomes separate and are pulled toward opposite ends of the dividing cell.

Question 2

anaphase-promoting complex

Answer 2

A protein complex that triggers the separation of sister chromatids and orchestrates the carefully timed destruction of proteins that control progress through the cell cycle; the complex catalyzes the ubiquitylation of its targets.

Question 3

aster

Answer 3

Star-shaped array of microtubules emanating from a centrosome or from a pole of a mitotic spindle.

Question 4

Bcl2 family

Answer 4

Related group of intracellular proteins that regulates

apoptosis; some family members promote cell death, others inhibit it.

Question 5

bi-orientation

Answer 5

The symmetrical attachment of a sister-chromatid pair on the mitotic spindle, such that one chromatid in the duplicated chromosome is attached to one spindle pole and the other is attached to the opposite pole.

Question 6

caspase

Answer 6

One of a family of proteases that, when activated, mediates the destruction of the cell by apoptosis.

Question 7

Cdk (cyclin-dependant protein kinase)

Answer 7

Enzyme that, when complexed with a regulatory cyclin protein, can trigger various events in the cell-division cycle by phosphorylating specific target proteins.

Question 8

Cdk inhibitor protein

Answer 8

Regulatory protein that blocks the assembly or activity of cyclin–Cdk complexes, delaying progression primarily through the G1 and S phases of the cell cycle.

Question 9

cell cycle

Answer 9

The orderly sequence of events by which a cell duplicates its contents and divides into two.

Question 10

cell-cycle control system

Answer 10

Network of regulatory proteins that govern the orderly progression of a eukaryotic cell through the stages of cell division

Question 11

centrosome

Answer 11

Microtubule-organizing center that sits near the nucleus in an animal cell; during the cell cycle, this structure duplicates to form the two poles of the mitotic spindle.

Question 12

centrosome cycle

Answer 12

Process by which the centrosome duplicates (during interphase) and the two new centrosomes separate (at the beginning of mitosis) to form the poles of the mitotic spindle.

Question 13

chromosome condensation

Answer 13

Process by which a duplicated chromosome becomes packed into a more compact structure prior to cell division.

Question 14

cohesin

Answer 14

Protein complex that holds sister chromatids together after DNA has been replicated in the cell cycle.

Question 15

condensin

Answer 15

Protein complex that helps
configure duplicated chromosomes for segregation by making them
more compact.

Question 16

cyclin

Answer 16

Regulatory protein whose concentration rises and falls at specific times during the eukaryotic cell cycle; cyclins help control progression from one stage of the cell cycle to the next by binding to cyclin-dependent protein kinases (Cdks).

Question 17

cytokinesis

Answer 17

Process by which the cytoplasm of a plant or animal cell divides in two to form individual daughter cells.

Question 18

G1-Cdk

Answer 18

Protein complex whose activity drives the cell through the first gap phase of the cell cycle; consists of a G1 cyclin plus a cyclin-dependent protein kinase (Cdk).

Question 19

G1-cyclin

Answer 19

Regulatory protein that helps drive a cell through the first
gap phase of the cell cycle and toward S phase.

Question 20

G1 phase

Answer 20

Gap 1 phase of the eukaryotic cell cycle; falls between the end of cytokinesis and the start of DNA synthesis.

Question 21

G2 phase

Answer 21

Gap 2 phase of the eukaryotic cell cycle; falls between the end of DNA synthesis and the beginning of mitosis.

Question 22

G1/S-Cdk

Answer 22

Protein complex whose activity triggers entry into S phase of the cell cycle; consists of a G1/S cyclin plus a cyclindependent protein kinase (Cdk).

Question 23

G1/S cyclin

Answer 23

Regulatory protein that helps to launch the S phase of the

cell cycle

Question 24

growth factor

Answer 24

Extracellular signal molecule that stimulates a cell to
increase in size and mass. Examples include epidermal
growth factor (EGF) and platelet-derived growth factor (PDGF).

Question 25

interphase

Answer 25

Long period of the cell cycle between one mitosis and the

next. Includes G1 phase, S phase, and G2 phase.

Question 26

kinetochore

Answer 26

Protein complex that assembles on the centromere of a condensed mitotic chromosome; the site to which spindle
microtubules attach.

Question 27

M-Cdk

Answer 27

Protein complex that triggers the M phase of the cell cycle; consists of an M cyclin plus a mitotic cyclin-dependent 
protein kinase (Cdk).

Question 28

M cyclin

Answer 28

Regulatory protein that binds to mitotic Cdk to form M-Cdk,

the protein complex that triggers the M phase of the cell cycle.

Question 29

M phase

Answer 29

Period of the eukaryotic cell cycle during which the nucleus and cytoplasm divide

Question 30

metaphase

Answer 30

Stage of mitosis in which chromosomes are properly

attached to the mitotic spindle at its equator but have not yet segregated toward opposite poles.

Question 31

mitogen

Answer 31

An extracellular signal molecule that stimulates cell

proliferation.

Question 32

mitosis

Answer 32

Division of the nucleus of a eukaryotic cell

Question 33

mitotic spindle

Answer 33

Array of microtubules and associated molecules that forms between the opposite poles of a eukaryotic cell during mitosis and pulls duplicated chromosome sets apart.

Question 34

phragmoplast

Answer 34

In a dividing plant cell, structure made of microtubules and
membrane vesicles that guides the formation of a new cell wall

Question 35

programmed cell death

Answer 35

A tightly controlled form of cell suicide that allows cells that are unneeded or unwanted to be eliminated from an adult or developing organism; the major form is called apoptosis.

Question 36

prometaphase

Answer 36

Stage of mitosis in which the nuclear envelope breaks down and duplicated chromosomes are captured by the spindle microtubules; precedes metaphase.

Question 37

prophase

Answer 37

First stage of mitosis, during which the duplicated

chromosomes condense and the mitotic spindle forms.

Question 38

S-Cdk

Answer 38

Protein complex whose activity initiates DNA replication; consists of an S cyclin plus a cyclin-dependent protein
kinase (Cdk)

Question 39

S cyclin

Answer 39

Regulatory protein that helps to launch the S phase of the

cell cycle

Question 40

S phase

Answer 40

Period during a eukaryotic cell cycle in which DNA is

synthesized.

Question 41

sister chromatid

Answer 41

Copy of a chromosome, produced by DNA replication, that remains bound to the other copy.

Question 42

spindle pole

Answer 42

Centrosome from which microtubules radiate to form the mitotic spindle

Question 43

telophase

Answer 43

Final stage of mitosis in which the two sets of separated chromosomes decondense and become enclosed by a nuclear envelope.

Question 44

apoptosis

Answer 44

A tightly controlled form of programmed cell death that
allows excess cells to be eliminated from an adult or
developing organism.

Question 45

contractile ring

Answer 45

Structure made of actin and myosin filaments that forms a

belt around a dividing cell, pinching it in two.

Question 46

p53

Answer 46

Transcription regulator that controls the cell’s response to
DNA damage, preventing the cell from entering S phase
until the damage has been repaired or inducing the cell to
commit suicide if the damage is too extensive; mutations in
the gene encoding this protein are found in many human
cancers.

Question 47

survival factor

Answer 47

Extracellular signal molecule that must be present to

suppress apoptosis.