Mitosis Flashcards
Sister chromatids are linked by _______, which are composed of 4 subunits: 2 _________ subunits and 2 _________ subunits.
Cohesins
Coiled-coil
Globular
What cyclin/CDK complex mediates the transition from G2 to M?
Cyclin B/CDK1 or the M-cyclin/CDK complex
Why do cyclin B levels increase steadily through G2? In other words, what causes cyclin B activity to increase?
The activity of cyclin A/CDK2 or the S-cyclin/CDK complex
Cyclin B/CDK1 activity is __________ controlled and only increases at the _____ transition.
Tightly
G2/M
Cyclin-dependent kinase 1 is subject to two phosphorylations at the onset of mitosis: one _______________, one _____________.
Inhibiting
Activating
How many phosphorylations does cyclin-dependent kinase 1 experience at the onset of mitosis?
Two
What kinase phosphorylates and inhibits cyclin-dependent kinase 1 at the onset of mitosis?
Wee1 kinase
____________ kinase phosphorylates and _________ cyclin-dependent kinase 1 at the onset of ____________.
Wee1 kinase
Inhibits
Mitosis
The phosphate added by wee1 kinase must be removed for mitosis to move forward. What phosphatase accomplishes this?
Cdc25 phosphatase
What must occur to activate cyclin-dependent kinase 1 so that mitosis can occur?
The inhibitory phosphate installed by Wee1 kinase must be removed by Cdc25 phosphatase
Cdc25 phosphatase must be _______________ in order to function.
Phosphorylated
Cdc 25 phosphatase is initiatlly activated by high cyclin ___/CDK ___ levels.
Cyclin A/CDK2
The majority of activation of Cdc25 phosphatase occurs via phosphorylation by cyclin ___/CDK ___.
Cyclin B/CDK1
Phosphorylation of Cdc25 phosphatase by cyclin B/CDK1 initiates a ____________ feedback loop for both Cdc25 and cyclin B/CDK1 activation.
Positive
Cyclin B/CDK1 phosphorylate Cdc25 phosphatase, activating it, and _______ kinase, inhibiting it, thereby activating even more cyclin B/CDK1
Wee1 kinase
In fission yeast, most growth occurs during ______ phase.
G2
Where is Wee1 kinase localized in the cell during mitosis in fission yeast?
Mid-point
What inhibits Wee1 kinase at the mid-point of the cell?
Cdr2
Pom1 is localized to the ______ of the cell and interferes with cdr2’s ability to inhibit Wee1 kinase.
Apex
What protein interferes with Cdr2 and thereby prevents its ability to inhibit Wee1 kinase?
Pom1
When cells are small, Pom1 is close enough to prevent Cdr2 from interacting with Wee1 kinasae. But as the cell elongates, _____ moves away from Cdr2 and ______, allowing _______ to bind and inhibit Wee1 kinase, thereby allowing for movement into mitosis.
Pom1
Wee1 kinase
Cdr2
When cells are small, _______ is close enough to cdr2, inhibiting its ability to inhibit ________ kinase. As the cell increases in size, ______ moves away from cdr2, which then inhibits __________ kinase and allows ________ to begin.
Pom1
Wee1 kinase
Pom1
Wee1 kinase
Mitosis
In Wee1 kinase ___________, cyclin B/CDK1 are not phosphorylated at the inhibitory site, meaning that CDK1 becomes active earlier in GS before sufficient growth has occured. This leads to cell division when the cells are still very _______.
Mutants
Small
What four things happen during mitosis?
- Chromosome condensation
- Nuclear envelope breakdown
- Mitotic spindle formation
- Sister chromatid separation and segregation
Downstream mitotic events of cyclin B/CDK1 are (1) chromosome ________________, (2) nuclear envelope ______________, (3) mitotic ______________ formation, and (4) sister chromatid separation/segregation.
Condensation
Breakdown
Spindle
The events of mitosis require both _______________ and ______________ kinases.
Polo-like kinase
Aurora kinases
_________________________ of condensins by cyclin B/CDK1 leads to ___________________ of chromosomes.
Phosphorylation
Condensation
Which protein is responsible for chromosome condensation?
Condensins
What protein phosphorylates condensins?
Cyclin B/CDK1
The nuclear ___________________ lines the inner surface of the nuclear envelope.
Lamina
The nuclear lamina is composed of three proteins. What are they?
- Lamin A
- Lamin B
- Lamin C
What phosphorylates and destabilizes lamins in the nuclear lamina?
CDK1
CDK1 _________________ and destrabilizes lamins of the nuclear ______________.
Phosphorylates
Lamina
CDK1 phosphorylates both lamins and ___________________.
Nuclear pore proteins
Phosphorylation of nuclear pore proteins by _____________ leads to nuclear pore protein ________________.
CDK1
Dissociation
In order for mitosis to continue, the nuclear ____________ must be broken down.
Envelope
The mitotic spindle arises from what type of cytoskeleton element?
Microtubules
What are astral microtubules?
Astral microtubules are a subpopulation of microtubules, which only exist during and immediately before mitosis. They are defined as any microtubule originating from the centrosome which does not connect to a kinetochore.
What are kinetochore microtubules?
Kinetochore microtubules attach the chromosomes to the spindle pole
What are interpolar microtubules?
Interpolar/Polar microtubules are a class of microtubules which also radiate out from the centrosome during mitosis. These microtubules radiate towards the mitotic spindle, unlike astral microtubules
Be familiar with this figure.
When does centrosome duplication occur?
Beginning of S phase
What cyclin/CDK complex does centrosome duplication require?
Cyclin E/CDK2
Centrosome duplication occurs at the beginning of _____ phase and requires cyclin ____/CDK____.
S phase
Cyclin E
CDK2
Centrosome separation does not occur until _________ and requires cyclin B/CDK1 and other kinases to occur.
Mitosis
Centrosome separation occurs in mitosis and requires cyclin B/CDK__ to occur.
Cyclin B/CDK1
Centrosome separation requires _____________ of centrosomal proteins by CDK1, ____________ kinases, and polo-like kinases.
Phosphorylation
Aurora kinases
Which three kinases are involved in centrosome separation?
- CDK1
- Aurora kinases
- Polo-like kinases