Cell cycle (cytokinesis) Flashcards
final stage in the cell cycle
cytokinesis
division of the cytoplasm in two.
cytokinesis
some cells undergo ____without cytokinesis and thereby acquire multiple nuclei.
mitosis
The first visible change of cytokinesis in an animal cell
appearance of a pucker, or cleavage furrow
The structure underlying furrow process
contractile ring
As the sister chromatids separate in anaphase, ____ and _____ II begin to
accumulate in the rapidly assembling
contractile ring
actin and myosin II
depends on formin (parallel arrays of
linear, unbranched actin filaments)
local formation of actin filaments
overlapping arrays of actin and myosin II
filaments ___ to generate the force
that divides the cytoplasm in two
contract
persists as a tether between
the two daughter cells and contains the
remains of the central spindle
midbody
a large protein structure derived from
the antiparallel interpolar microtubules
of the spindle midzone, packed tightly
together within a dense matrix material
central spindle
small GTPase of the Ras superfamily
RhoA
controls the assembly and function of the
contractile ring at the site of cleavage
RhoA
RhoA promotes:
actin filament formation, myosin II
assembly, and ring contraction at the cell
cortex
RhoA stimulates actin filament formation by
activating formins; activating multiple protein
kinase (Rock)
must occur only after the two sets of
chromosomes are fully segregated from each other
Cytokinesis
must be placed
between the two sets of daughter
chromosomes
site of division
depend on
mitotic spindle
correct timing and position
during anaphase, the spindle generates
signals that initiate ____ formation at a
position midway between the ____
___
furrow
spindle poles
Why cytokinesis also occurs
at the correct time
because dephosphorylation of Cdk substrates, which depends on cyclin destruction in metaphase and anaphase, initiates cytokinesis
How does the mitotic spindle specify the site of division?
- astral stimulation model
- central spindle stimulation model
- astral relaxation model
astral microtubules carry furrow-inducing
signals
astral stimulation model
the spindle midzone, or central spindle,
generates a furrow
-inducing signal that
specifies the site of furrow formation at
the cell cortex
central spindle stimulation model
the astral microtubules promote the
local relaxation of actin
–myosin bundles
at the cell cortex
astral relaxation model
cortical relaxation is minimal at the
spindle equator; promoting cortical
contraction
astral relaxation model
higher-plant cells are enclosed by a semirigid
cell wall
the cytoplasm of the plant cell is _____from the ____out by the _____ __ _ ___ ___ ____, called
the cell plate, between the two daughter nuclei
partitioned
inside
construction of a new cell wall ( cell plate)
The assembly of the
cell plate begins in
late anaphase and is guided by a structure called the phragmoplast
contains microtubules derived from the mitotic spindle
phragmoplast
each daughter cell must also inherit all of the other essential cell
components, including the membrane-enclosed organelles
process of mitosis
can arise only by the growth and division of the preexisting
organelles.
organelles
usually present in large
enough numbers;their numbers double once each cycle
mitochondria and chloroplasts
cut into two during cytokinesis
ER
reorganized and fragmented during mitosis
Golgi apparatus
cells divide asymmetrically to produce
two cells that ____ in size, in the
cytoplasmic contents they inherit, or in
both
different
the mother cell must first segregate ___ _____ _______ to one side of the cell
and then position the ___of ____
so that the appropriate daughter cell
inherits these components
cell fate determinants
plane of division
Some cells undergo multiple rounds of nuclear division without intervening _____ division.
cytoplasmic
first 13 rounds of nuclear division occur without cytoplasmic division
Drosophila embryo
A cell in which multiple nuclei share the same
cytoplasm is called a
syncytium
greatly speeds up early development
syncytium
membranes are created around each nucleus
in one round of coordinated cytokinesis
cellularization
Nuclear division without cytokinesis in some types of mammalian
cells
megakaryocytes, hepatocytes, heart muscle cells
