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Terms in this set (33)
In S phase, _________ is duplicated precisely. Mechanisms exist to ensure that it is completely duplicated, and not over duplicated.
_________ hold the duplicated chromatids together.
The single _______ is duplicated in preparation for M phase.
M phase consists of two distinct the overlapping parts: _______ and ________.
What is mitosis?
The precise an equal segregation of the duplicated chromosomes by the microtubule-based mitotic spindle
What is cytokinesis?
The division of the cytoplasm in two halves to generate two cells by contraction of the microfilament-based contractile ring
What is the mitotic spindle?
A machine to distribute the chromosomes equally with a built-in quality control system (the checkpoint)
What side of the microtubule is associated with the centrosome/spindle pole?
The spindle contains three classes of microtubules: ________, ________, and ________ microtubules.
Aster, kinetochore, and interpolar
What occurs in interphase?
Chromosome duplication and cohesion
What occurs in prophase?
Breakdown of interphase microtubule display and its replacement by mitotic asters
Mitotic aster separation
What occurs in prometaphase?
Nuclear envelope breakdown
Chromosomes captured, bi-oriented and brought to the spindle equator
What occurs in metaphase?
Chromosomes aligned at the metaphase plate
What is the function of condensins?
Help condense chromosomes to facilitate segregation during mitosis
What creates stable bipolar attachment?
What occurs to the kinetochore when stable microtubule attachment is achieved?
Kinetochore components dephosphorylated and cannot be dephosphorylated
How does the cell ensure that ALL chromosomes are bi-oriented?
The checkpoint at metaphase (mitosis)
What happens when the checkpoint in mitosis is satisfied?
The Anaphase Promoting Complex (APC) is activated, leading to degradation of M-cyclin and securin/cohesion holding chromatids together
What happens when there are unattached kinetochores on a chromosome?
They send out a signal preventing exit from metaphase
What occurs during anaphase?
APC activated and cohesins degraded
(Anaphase A) chromosome movement to poles
(Anaphase B) spindle pole separation
What occurs during telophase?
Nuclear envelope reassembly
Assembly of contractile ring
What occurs during cytokinesis?
Reformation of interphase microtubule array
Contractile ring forms cleavage furrow
How does Anaphase A work?
Shortening of kinetochore microtubules: forces are generated at kinetochores to move chromosomes toward their spindle pole
Depolymerization of plus end of kinetochore microtubules
How does Anaphase B work?
A sliding force (1) generated between interpolar microtubules from opposite poles to push the poles apart; a pulling force (2) acts directly on the poles to move them apart
The events in the cell cycle are ordered by ______ and driven by ________.
Checkpoints; cyclin-dependent kinases (Cdks)
What does a duplicated chromosome consist of?
Two chromatids, tightly joined at the centromere
During the S and G2 phases of the cell cycle, the ____________ duplicates, which will later become the _______________.
Interphase chromosome; poles of the mitotic spindle
What is a kinetochore?
A specific region associated with the centromeres to which the plus end of kinetochore microtubules can attach
Three classes of microtubules are involved in the mitotic spindle - all have their _______ ends associated with the spindle poles. One class - the _____ microtubules - extends out to the cell periphery. The second class - the ____________ microtubules - extend from the centrosome with their other end associated with a kinetochore. The third class - the _________ microtubules - extend from each pole and inter-digitate in the middle region of the spindle.
Minus; aster; kinetochore; interpolar
What is the function of Aurora B?
Phosphorylates kinetochore components at unattached kinetochores making microtubule attachment unstable
It is counterbalanced by a phosphatase that dephosphorylates the kinetochore components
How is cytokinesis different in animal and plant cells?
In animal cells, the formed contractile ring pinches the cell into two in a process known as cytokinesis
In plant cells, a contractile ring does not form, but rather Golgi derived vesicles localize between the nuclei and form a new cell wall
Much of what we know about the cell cycle comes from genetic analysis in fission yeast. Paul Nurse discovered Cdk in fission yeast, so you decide to try your hand at using this organism to see if Paul got the story right. Tony has told you that there are two phosphorylation sites on Cdk, an inhibitory site and an activating site. You mutate the inhibitory site in yeast Cdk so that it cannot be phosphorylated. Your mutant should be similar to:
Cells lacking the kinase Wee1
What do you think would happen over a period of time to a metaphase cell if you used a laser to keep cutting the kinetochore microtubules to just one chromosome?
The cell would not progress into anaphase
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