Chapter 18 Flashcards
anaphase
Stage of mitosis during which the two sets of chromosomes separate and are pulled toward opposite ends of the dividing cell.
anaphase-promoting complex
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.
aster
Star-shaped array of microtubules emanating from a centrosome or from a pole of a mitotic spindle.
Bcl2 family
Related group of intracellular proteins that regulates
apoptosis; some family members promote cell death, others inhibit it.
bi-orientation
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.
caspase
One of a family of proteases that, when activated, mediates the destruction of the cell by apoptosis.
Cdk (cyclin-dependant protein kinase)
Enzyme that, when complexed with a regulatory cyclin protein, can trigger various events in the cell-division cycle by phosphorylating specific target proteins.
Cdk inhibitor protein
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.
cell cycle
The orderly sequence of events by which a cell duplicates its contents and divides into two.
cell-cycle control system
Network of regulatory proteins that govern the orderly progression of a eukaryotic cell through the stages of cell division
centrosome
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.
centrosome cycle
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.
chromosome condensation
Process by which a duplicated chromosome becomes packed into a more compact structure prior to cell division.
cohesin
Protein complex that holds sister chromatids together after DNA has been replicated in the cell cycle.
condensin
Protein complex that helps
configure duplicated chromosomes for segregation by making them
more compact.
cyclin
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).
cytokinesis
Process by which the cytoplasm of a plant or animal cell divides in two to form individual daughter cells.
G1-Cdk
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).
G1-cyclin
Regulatory protein that helps drive a cell through the first
gap phase of the cell cycle and toward S phase.
G1 phase
Gap 1 phase of the eukaryotic cell cycle; falls between the end of cytokinesis and the start of DNA synthesis.
G2 phase
Gap 2 phase of the eukaryotic cell cycle; falls between the end of DNA synthesis and the beginning of mitosis.
G1/S-Cdk
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).
G1/S cyclin
Regulatory protein that helps to launch the S phase of the
cell cycle
growth factor
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).
interphase
Long period of the cell cycle between one mitosis and the
next. Includes G1 phase, S phase, and G2 phase.
kinetochore
Protein complex that assembles on the centromere of a condensed mitotic chromosome; the site to which spindle
microtubules attach.
M-Cdk
Protein complex that triggers the M phase of the cell cycle; consists of an M cyclin plus a mitotic cyclin-dependent protein kinase (Cdk).
M cyclin
Regulatory protein that binds to mitotic Cdk to form M-Cdk,
the protein complex that triggers the M phase of the cell cycle.
M phase
Period of the eukaryotic cell cycle during which the nucleus and cytoplasm divide
metaphase
Stage of mitosis in which chromosomes are properly
attached to the mitotic spindle at its equator but have not yet segregated toward opposite poles.
mitogen
An extracellular signal molecule that stimulates cell
proliferation.
mitosis
Division of the nucleus of a eukaryotic cell
mitotic spindle
Array of microtubules and associated molecules that forms between the opposite poles of a eukaryotic cell during mitosis and pulls duplicated chromosome sets apart.
phragmoplast
In a dividing plant cell, structure made of microtubules and
membrane vesicles that guides the formation of a new cell wall
programmed cell death
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.
prometaphase
Stage of mitosis in which the nuclear envelope breaks down and duplicated chromosomes are captured by the spindle microtubules; precedes metaphase.
prophase
First stage of mitosis, during which the duplicated
chromosomes condense and the mitotic spindle forms.
S-Cdk
Protein complex whose activity initiates DNA replication; consists of an S cyclin plus a cyclin-dependent protein
kinase (Cdk)
S cyclin
Regulatory protein that helps to launch the S phase of the
cell cycle
S phase
Period during a eukaryotic cell cycle in which DNA is
synthesized.
sister chromatid
Copy of a chromosome, produced by DNA replication, that remains bound to the other copy.
spindle pole
Centrosome from which microtubules radiate to form the mitotic spindle
telophase
Final stage of mitosis in which the two sets of separated chromosomes decondense and become enclosed by a nuclear envelope.
apoptosis
A tightly controlled form of programmed cell death that
allows excess cells to be eliminated from an adult or
developing organism.
contractile ring
Structure made of actin and myosin filaments that forms a
belt around a dividing cell, pinching it in two.
p53
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.
survival factor
Extracellular signal molecule that must be present to
suppress apoptosis.
