Cell Division

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Requirements for cell division
- 1. Grow; build new macromolecular structures
- 2. Duplicate genetic material (DNA replication)
- 3. Partition/Segregate gentic material (mitosis)
- 4. Divide content of cytoplams (cytokinesis)
Batterial Cell Divison
- Simple process produces two cell from one
- Made easier by single circular chromosome
- Binary fission
- Proteins involved similar to eukaryotic proteins
- Process is distinct and different from mitosis
Key Feature of Bacterial Division
- Replication and segregation concerted process (simultaneous process)
- -chromosome is "pushed" to poles during replication
- -chromosome finish replication at opposite poles
- Exact mechanism of segregation not known
Eukaryotic Cell Division
- More complex genome, mutiple chromosomes
- Genome inside nucleus
- More complex cytoplasmic contents
How does cell keep track of chromosomes?
- Keep products of replication together (protein glue)
- Temporal separation and replication/segregation
Cell Cycle
G₁

Gap 1 prepares for DNA replication
Cell Cycle
S

During synthesis DNA is replicated
Cell Cycle
G₂

Gap 2 prepares for mitosis
Cell Cycle
M

Mitosis segragate chromosomes
Interphase
- G₁
- S
- G₂
M Phase
- Mitosis
- Cytokinesis
G₀

Cells have left the cycle: noncycling
Eukaryotic Chromosomes
- Linear structure that contain single DNA molcule
- DNA molecule is always packaged into chromosomes
- Amount of dondensation changes during cell cycle
- Chromosome has visible contriction called centromere
Nucleosomes

1st DNA wrapped around protein
Centromere
- Visible contriction
- -Site where replicated chromosomes held together
- -Site of kinetochore: functional element of centromere
Phases of Mitosis
- Divide into 5 phases
- -Prophase
- -(Prometaphase)
- -Metaphase
- -Anaphase
- -Telophase
What is the function of mitosis
- To segregate chromosomes
- -Each cell gets 1 copy each chromosome
Does cell count or mark chromosomes?

No!
How do we ensure new cells gets entire genome?
- Keep chromosomes together after replication
- Align them together in the center of cell
- Pull apart copies at the same time
- Completely rearranging microtubles
- -Construct spindle to separate chromosome
Prophase

Chromosome condense; nucleus breaks down, spindle forms (microtubles)
Metaphase

Chromosomes move to center of cell, attached to spindle at equator
Anaphase

Chromosome are pulled to poles
Telophase

Reverse of prophase
Cytokinesis
- Cell is actually divided
- -Centractile ring of microfilaments
Control of cell cycle
- Cancer: uncontrolled cell division
- Irreversible events
- -DNA replication
- -Anaphase
- To insure accuracy cell monitors process
MOC: Positive regulators that drive cell cycle
- Cyclin proteins are produced in synchrony with cycle
- Cyclin dependent kinases (cdk) drive cycle
MOC: Checkpoints
- Are points the cell assess accuracy
- Allows cell to stop if process is faulty
- Can even lead to cell death when process goes wrong
CP: G₁/s
- Decision to replicate DNA
- Check for chromosome integrity
CP: G₂/M
- Is replication complete?
- Are the chromosomes damaged:
Metaphase/Anaphase
- Decision to separate chromosomes
- -All chromosomes align properly
- -Connected to both poles

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skyy22

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Card Set

Cell Division

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Cell division flashcards

Updated

2010-09-23T17:53:03Z

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