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Cell Division. Cell divides into two daughter cells. Revised 10-09-2006. Cell Cycle. G 1 phase Cellular Growth Development S phase DNA Replication Protein synthesis G 2 phase Synthesis of organelles Materials for cell division M Phase Mitosis. Length of the Cell Cycle. - PowerPoint PPT Presentation
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Cell DivisionCell divides into two daughter cells
Revised 10-09-2006
Cell CycleG1 phase
•Cellular Growth •Development
S phase •DNA Replication •Protein synthesis
G2 phase •Synthesis of organelles •Materials for cell division
M Phase•Mitosis
Length of the Cell Cycle
• Intestine•24-48 hours
• Frog embryo•1 hour
Control of the Cell Cycle
• Cyclins
• Cyclin Dependent Kinases
Cell Cycle Regulation
The cyclins are named “cyclins”
because their appearance during the cell cycle is cyclical
Cyclins/Kinases Complexes
G1 phase Cellular Growth and Development
Cyclin DCDK4CDK6
Cyclin ECDK 2
Checkpoint 1•Cell size?•DNA?
Cyclin D
cyclin D-dependent kinase Cdk6
S phase DNA Replication and Protein synthesis
Cyclin ACDK 2
Cyclin A
• Residues 173-432• 2 similar domains• Cyclin fold
–5 α-helices
CDK 2• Domain 1
–85 residues
–1 α-helix
–5 stranded β-sheet
• Domain 2
–213 residues
–α-helices
Cyclin A/CDK 2 Complex
Cyclin A/CDK 2 Complex
Inactive Active
G2
• Cyclin B
Checkpoint 2•All DNA Duplicated? •Cell size?•All DNA Intact?•Repair DNA
Cell Cycle RegulationM-phase promoting Factor MPF
Checkpoint 3•Chromosomes attached to spindle fibers?
Mitosis
.• Process by which the nucleus of
the cell is divided into two nuclei, each with the same number and kinds of chromosomes as the parent cell.
• Cytokinesis is the process by which the cytoplasm is divided.
Chromosomes
ProphaseLongest (50 - 60%)
• Appearance of chromosomes• Nucleolus disappears• Nuclear membrane breaks down• Centrioles separate and migrate to
opposite poles of cell
MetaphaseShortest
• Chromosomes line up across center of cell
• Spindle fibers form from centrioles to centromere
Anaphase
• Sister Chromatids split at Centromere
• Individual Chromosomes move toward poles
TelophaseFinal Phase
• Spindle fibers breakdown• Chromosomes uncoil into Chromatin• Nuclear envelope reforms• Nucleolus becomes visible
Mitosis in Whitefish and Onion
PROPHASE METAPHASE ANAPHASE TELOPHASE
Cytokinesis
The process by which the cytoplasm divides, forming two new cells.
Cytokinesis
• Animals •Cell membrane •pinches inward
• Plants•Cell plate
The process by which the cytoplasm divides, forming two new cells.
Result of Cell Division
Two cells that are identical to each other.