The Cell Cycle 15 October, 2003 Text Chapter 12. Cell division functions in reproduction, growth,...
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Transcript of The Cell Cycle 15 October, 2003 Text Chapter 12. Cell division functions in reproduction, growth,...
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The Cell Cycle15 October, 2003Text Chapter 12
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Cell division functions in
reproduction, growth, and
repair
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genome: all of a cell’s DNA
chromosome: individual DNA molecule
chromatin: chromosomal DNA and its protein scaffold
sister chromatids: the two identical copies of a duplicated chromosome
centromere: the point of attachment for two sister chromatids
somatic cells: (most cells) have two copies of each chromosome (diploid)
gametes: (reproductive cells; sperm and eggs) have one copy of each chromosome (haploid)
Important Terms (part one)
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cell cycle: the process of cell division
mitosis (M phase) nuclear division
interphase: the main part of the cell cycle
G1 phase - cell prepares for DNA synthesis, usually grows in size
S phase - DNA is duplicated
G2 phase - cell checks fidelity of DNA replication, prepares for nuclear division
mitosis subphases - prophase, prometaphase, metaphase, anaphase, telophase
cytokinesis
More Important Terms
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Mitosis (1)
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Mitosis (2)
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The mitotic spindle is composed of microtubules, and directs the alignment of chromosomes on the metaphase plate.
During anaphase, the microtubules attached to each centromere guide the movement of chromosomes toward spindle poles.
The Mitotic Spindle
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Polar Depolymerization of Microtubules
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Microfilaments contract to divide the cytoplasm. Plant cells are less flexible, because of the cell wall, and deposit cell wall material between the two daughter cells.
Cytoplasmic Division
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Mitosis (differential staining)
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Mitosis in Growing Tissue
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Binary Fission in Bacteria
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Evolution of Mitosis
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The cell’s place in the cell cycle is signaled by the presence or absence of cell cycle kinases.
A growth signal leads to passage through the G0
restriction point into G1. (See Fig 11.11)
The cell then executes a programmed series of steps that culminate in mitosis and cytokinesis.
Cell Cycle Control
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is an example of kinase control of the cell cycle. It is like a license that allows the cell to begin M phase of the cell cycle.
MPF is a two-subunit enzyme. One subunit is Cdk (present during the whole cell cycle). The other subunit is a cyclin protein that builds up as M phase approaches.
When the cyclin concentration is high enough, cyclin binds to Cdk, forming the MPF enzyme. MPF activity signals the start of mitosis.
MPF
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Normal cells are transformed to tumor cells when cell division is not controlled.
Cancer cells are growth-factor independent.
Cancer cells have escaped density-dependent inhibition.
Most cancerous cells are destroyed by the immune system, but some cells progress from benign to malignant, and possibly to metastatic.
Cancer
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Cell Culture and Growth Factors
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Density-dependent inhibition is a property of normal cells.
Cancer cells lack this inhibition.
Density-dependent Inhibition
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Metastatic cancer cells spread throughout the body.
Metastatic Cancer
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