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Mitosis
The division of the nucleus in a eukaryotic cell
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Interphase consists of what cell phases
G1 Phase-------S phase-------- G2 Phase
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G0 Phase
A dormant phase when nothing is happening, can stay here for its life (neurons are always here)
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What are the two major checkpoints in a cell cycle
- G1 Checks to make sure the environment is favorable and that the DNA is intact before starting the S phase
- G2 Checks to see if the DNA intact, and if it is all replicated
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Which cell phase is the shortest
The Mitosis phase
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What is the S phase
It is when the DNA is synthesized and lasts about 8 hrs
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List the phases of mitosis in order
- 1. Preprophase
- 2. Prophase
- 3. Metaphase
- 4. Early Anaphase
- 5. Late Anaphase
- 6. Telophase
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What happens in Preprophase
Intranuclear condensation of chromosomes
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Prophase
- 1. Individualization of chromosomes
- 2. Initiation of mitotic spindle and its completion
- 3. A disappearance of the nuclear envelope and nucleolus
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Metaphase has what characteristics
Chromosomes are arranged in a center, the spindle is completed, and there is a disappearance of the nuclear envelope and nucleolus
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Early Anaphase
Splitting of chromosomes and migration to poles
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Late Anaphase
- Chromosome at poles
- Beginning of cell division, and cleavage furrow
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Telophase
- Nuclear completion
- Nucleolar formation
- End of cell division
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What are the two important proteins for mitosis and their function
- Cohesins (link sister chromatids)
- Condensins (link DNA into the condensed coil)
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What does a cohesin do and what phase doesn't contain it
Cross links two adjacent sister chromatids, gluing them together (degraded at the beginning of anaphase allowing the sisters to come apart)
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Condensins do what and is active when
Mediate intramolecular cross linking to coil DNA in the process of chromosome condensation (Active at the beginning of prophase)
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MT's are favorite targets for anti cancer drugs why
They are used to stop the division of cancer cells
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Taxol (Paclitaxel)
- A drug that binds tightly to MT's and stabilizes them
- (Cells that are effected undergo apoptosis)
- Chemo!!
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Intermediate filaments in mitosis
Control the breakdown and reformation of the nuclear envelope
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What happens to organelles at mitosis
- ER and Golgi vesiculate and then reform at telophase
- Nothing happens to the Mitochondria, peroxisomes and Lysosomes
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What happens to other functions during mitosis
They pretty much all just stop
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What triggers the disassembly of the nuclear lamina and the nuclear envelope
Phosphorylation of lamina
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Mitosis and Cytokenisis take place during what cell cycle phase
The M phase
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DNA replication happens during what phase
S Phase
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In what order are the cell phases
G2 - M - G1 - S
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What is telophase
As the nuclear envelope forms around each pair of chromatids, the nucleoli reappear
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What is the kinetocore
It is the binding site of the MT's at the centromere of the chromosome
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Anaphase A vs Anaphase B
- Anaphase A, Chromosomes move to poles
- Anaphase B, Seperation of the poles themselves
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What is the job of the motor proteins
They move the MT's between each other leading the chromosomes to the cell poles
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What two places are the poles located
On the wall of the cell at the pole ends, and near the center working antiparallel to the MT's next to them
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Anaphase A depends on
Motor proteins at the kinetocore
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Anaphase B depends on
- Motor proteins at the poles that pull them apart from each other
- On motor proteins in the central spindle
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The motor proteins in between the microtubules have what effect
- They are located at the point where the microtubules overlap and they force them to their respective poles
- They are (+) end directed motor proteins
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The motor proteins at the poles have what effect
They pull the centrioles towards the poles and away from each other. They are a (-) end directed motor protein
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What is the role of actin in mitosis
Along with myosin 2 they form the contractile ring separating the new cells
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