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57 Cards in this Set
- Front
- Back
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what is the partitioning of the chromosomes duplicated in the S phase into two daughter cells?
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mitosis
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what is the division of cytoplasm into two daughter cells at the end of mitosis?
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cytokinesis
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mitosis is subdivided into what 6 primary phases?
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prophase
prometaphase (early and late) metaphase anaphase telophase cytokinesis (early and late) |
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1. Prophase-Prometaphase
-Cdk1 kinase (Cdk1-cyclin B) -... of replicated sister chromatids -disassembly of nuclear ... and Golgi -reorganization of ... (attachment of microtubule at kinetochores) |
condensation
envelope cytoskeleton |
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2. Metaphase-anaphase
-bipolar attachment of chromosomes to ... -proteolytic network destroys proteins holding sister chromatids together; Cdk1 ... -... of sister chromatids; movement to opposite poles |
spindle
inactivated separation |
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3. Telophase-cytokinesis
-... of two daughter nuclei -nuclei and surrounding cytoplasm partitioned by cytokinesis by contraction of ... ring -... may overlap with anaphase and telophase |
reformation
actin-myosin cytokinesis |
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what is the process of centrosome duplication and separation called?
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centrosome cycle
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Prior to mitosis, in the S phase, two events occur:
1. DNA ... 2. Duplication of the ... (major microtubule organizing centers) |
replication
centrosome |
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Duplication of the Centrosome- begins in S phase, completed in G2 phase
-MTOC -form the two ... of the mitotic spindle; responsible for separation of the duplicated chromosomes -important for each daughter to receive their own centrosome -duplication driven by same Cdks that trigger DNA ... |
poles
replication |
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Development of the asters
-at the onset of mitosis, separation of centrosomes and nucleation of radial array of ... forming an aster -two asters move to opposite sides of nucleus forming poles of mitotic spindle -spindle microtubules capture chromosomes when nuclear envelopes disassembled |
microtubules
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Two proteins important in the condensation of chromosomes (work together to reduce mitotic chromosomes to small, condensed structures:
1. Condensin -assembly triggered by Cdk-1 kinase during mitosis -accumulation on DNA facilitates ... -condensation makes chromosomes more compact and easier to segregate 2. Cohesin -assemble along the length of each chromatid during replication -hold sister chromosomes together through mitosis until anaphase -crucial for proper ... |
condensation
segregation |
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which protein coils up single DNA molecule?
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condensin
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which protein holds sister chromatids together?
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cohesin
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Hallmark of Prophase:
-chromosome ... into two sister chromatids -driven by ... of proteins associated with mitotic chromosomes |
condensation
phosphorylation |
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prophase:
-Transition from G2 into ... -Chromosomes begin to ... (hallmark) -Disassembly of ... (do not see disassembly of nuclear envelope) -Conversion of interphase microtubule network into ... |
mitosis
condense nucleolus asters |
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Cytoskeleton Reorganization
-majority of cytoskeletal reorganization occurs during ... -shift of extensive permeating microtubule network into short, radial arrays called ... -microtubules radiate from the asters which are found in the ... -the aster migrate across surface of nuclear envelope; start of ... assembly |
prophase
asters centrosomes spindle |
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(prophase)
Cdk1 kinase phosphorylation: -stops transcriptional machinery - halts protein synthesis and assembly of new ribosomes -causes disassembly of ... |
nucleolus
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(prophase)
-... of Golgi apparatus and ER -Decrease in membrane-mediated events (intracellular sorting of membrane components, endocytosis and exocytosis) |
Vesiculation
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what is this?
-allows for orientation to occur -trilaminar disk that form at the centromere region of chromosome |
kinetochore
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... kinetochore continuous with centromeric heterochromatin
... kinetochore consisting of an outer plate with a fibrous corona (dynein motors-move along microtubule towards negative end) -microtubule binding |
inner
outer |
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-each sister chromatid has a kinetochore; sister kinetochores located on ... faces of mitotic chromosome
-... attach to kinetochore in fiber bundles -orientation: only one of the two sister chromatid will face a given spindle pole at any one time |
opposite
microtubule |
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what are the 3 classes of microtubules that are important in movement?
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aster, kinetochore, and interpolar microtubules
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1. Kinetochore microtubules
-plus ends embedded in kinetochore in ..., minus ends at ... -characteristic kinetochore fibers -allow for the ... of the sister chromatids |
chromosomes
spindle pole separation |
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2. Interpolar microtubules
-found throughout mitotic spindle -do not attach to kinetochore -minus ends terminate near poles; interdigitated (cross over), antiparallel microtubules form the central spindle (cytokinesis) -do not interact with anything but ... |
one another
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3. Astral microtubules
-project out from poles; same polarity, ... ends proximal to poles -orient spindle in the cell |
minus
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What is this?
each unit of a spindle pole, associated kinetochore and interpolar and astral microtubules |
half spindle
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Early Prometaphase:
-breakdown of ... makes chromosomes accessible to microtubules -microtubules assemble/disassemble searching for ... -chance encounter of ... ends of microtubules with kinetochores allows for ‘capture’ |
envelope
chromosomes plus |
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Late Prometaphase:
-’capture’ of the microtubule by the kinetochore results in the movement of chromosome toward the spindle pole from which the microtubule ... -chromosome attached at one pole ‘hitches’ a ride along the kinetochore fiber of a chromosome aligned at equator -’capture’ microtubule from ... poles -chromosomes with both kinetochores attached to both poles move to ... of spindle |
originated
opposite middle |
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Spindle checkpoint:
-you cannot progress to ... until every last chromosome is attached at opposite poles -Not turned off until the last chromosome properly forms a ... attachment -corrects ... errors -loss leads to genetic imbalance called ... |
metaphase
bipolar attachment aneuploidy |
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What are these?
1. One or both kinetochores lacking attached microtubules 2. Attachment of both sister kinetochores to same spindle pole (rare) 3. Single kinetochore attached simultaneously to both spindle poles (most common) |
Common errors in early and late prometaphase
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metaphase:
-Chromosomes positioned at middle of spindle called the ... -... movement along equator due to motor proteins and fluctuations in kinetochore microtubules -Destruction of cyclin B and securin by ... |
metaphase plate
Oscillatory APC/C (anaphase promoting complex) |
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APC/C:
-Inactivation of CDK-1 as cyclin B is destroyed by APC/C. -Destroys securin which inhibited separase -Separase is the enzyme responsible for liberating ... -In turn initiates the separation of the sister chromatid - Separation will be complete in anaphase |
cohesin
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Counteracting forces
Elongation of the spindle poles involves the interpolar microtubules and the aster microtubules outward force generated by ... and bipolar kinesin-5 -dynein moves toward the aster microtubule minus ends, pulling poles OUT towards the cell cortex -kinesin-5 moves toward the interpolar microtubule plus ends, pushing the poles apart inward force generated by kinesin-14 (counterbalance) and interpolar microtubules disassembly -kinesin-14 moves toward the interpolar microtubule minus ends, pulling the poles together |
dynein
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Anaphase:
Anaphase A -Sister chromatids move to opposite spindle poles Anaphase B -Poles move apart Preparation for ... -cell cortex activated by mitotic spindle |
cytokinesis
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Anaphase
-abruptly begins when the ... linkages that hold the sister chromatids together are released -each chromatid is pulled to the spindle pole -this segregates the identical set of daughter chromosomes to the ... ends of the spindle -preps for cytokinesis |
cohesin
opposite |
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movement of the daughter chromosomes are a result of what 2 independent processes that occur simultaneously?
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Anaphase A
Anaphase B |
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Separation of sister chromatids
-regulated by ..., not the mitotic spindle |
chromosomes
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Three factors that regulate separation:
1. ... -ring-like structure that holds sister chromatids together 2. ... -protease that digests cohesin 3. ... -inhibitor of separase |
Cohesin
Separase Securin |
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Remember! After last chromosome forms bipolar attachment to spindle poles, spindle checkpoint is ...
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switched off
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1. APC/C tags securin with Ub
-securin destroyed by proteaosomes throughout metaphase -securin falls below critical level 2. ... free to cleave cohesin -sister chromatids able to separate from each other |
Separase
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Remember! Separation of sister chromatids can ONLY happen after ... has been cleaved.
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cohesin
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Anaphase A (sister chromatids move to opposite spindle poles)
-movement the results of collaborative effort between dynein molecules and microtubule disassembly -..., which are attached to the kinetochore outer plate, ‘run’ toward poles -dynein hold onto disassembling microtubules -kinetochore microtubule disassembly moves chromosomes toward poles |
dynein
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Anaphase B (spindle poles move apart)
-elongation and sliding of ... microtubules |
interpolar
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Three factors contribute to lengthening:
1. Microtubule growth at plus ends of interpolar microtubules 2. Sliding force generated between interpolar microtubules by ... 3. Movement of spindle poles with attached kinetochore microtubules away from interpolar microtubules |
kinesin
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Anaphase ...:
-dynein ‘runs’ towards the spindle poles (minus ends) (ahead of kinetechore disassembly) -kinetochore microtubules disassemble behind the motor protein |
A
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Anaphase ...:
-assembly of interpolar microtubules at plus ends - dominate plus-end directed movement by kinesin -kinesin molecules attach to adjacent anti-parallel microtubules causing them to slide across each other -spindles poles physically separate |
B
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Organization of the Central Spindle:
-occurs in Anaphase ... -stabilized by amorphous dense material called stem body matrix -maintains the microtubules in ... position and holds the half spindles together -house several proteins that regulate cytokinesis |
B
antiparallel |
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Telophase:
-Reassembly of ... around the two set of chromosomes (identical) -Cell prepares for division: mitotic ... determines the plane of cleavage as well as the timing of cytokinesis |
nuclear envelope
spindle |
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Telophase
Hallmark: Reformation of the ... In addition to a full complement of chromosome, each daughter cell must receive essential cell components -membrane-bound organelles are inherited -grow and divide from pre-existing organelles |
nuclear envelope
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Nuclear envelope disassembly
-occurs during ... -CDK-1 triggers phosphorylation of lamins causing disassembly of ... -nuclear envelope dissociates into vesicles (in ...) |
prophase
nuclear lamina prometaphase |
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Nuclear envelope reassembly :
begins in anaphase, completed in telophase reassociation of nuclear pore complex in envelope nuclear lamina reassembly triggered by removal of ... groups on lamin subunits -lamin subunits disassembled early in prophase are recycled -lamins are targeted to surface of chromosomes nuclear envelope re-forms -nuclear proteins pumped in -decondensation of chromosomes -transcription resumes |
phosphate
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Hallmark of cytokinesis is the division of the ... into 2 daughter cells
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cytoplasm
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Early cytokinesis (Formation of the ...)
-cytokinesis achieved by contractile ring -ring consists of actin and myosin II -actomyosin organization resembles that of smooth muscle -ring position dictated by signals from central spindle proteins and cell cycle machinery |
contractile ring
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Late cytokinesis (... of cells)
contraction of cleavage furrow reducing cytoplasm into thin intercellular bridge -midbody at center which contains centriolin -centriolin is ultimately responsible for separation of cells by fusing plasma membrane of individual cells (mechanism unknown) re-establishment of adherence to substratum -extracellular matrix -neighboring cells re-establishment of cytoskeleton |
Separation
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Cleavage Furrow
-first visible sign of ... -development of furrow driven by contraction of ... -furrow runs ... to central spindle (long axis of mitotic spindle) -seen as early as anaphase -regulated-does not begin until sister chromatids separate (because it could damage the DNA) -cuts between the two groups of segregated daughter chromosomes -each daughter cell receives an identical and complete set |
cytokinesis
contractile ring perpendicular |
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Assembly of the contractile ring occurs early in ...
-actual stimulus unknown -series of overlapping ... filaments -plus ends (barb ends) attach to plasma membrane around equator -interdigitation of myosin II (filamentous form) -myosin II pulls actin filaments into ring around equator -contractile force is generated by the sliding of actin filaments against myosin filaments |
anaphase
actin |
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Contractile ring is a transient structure
-assembled for cytokinesis -becomes ... as cytokinesis progresses -complete ... after cells separate |
smaller
disassembly |
