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CellDivision Cell divides into two daughter cells Revised 10-09-2006
Cell Cycle • G1 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
G1 phaseCellular Growth and Development Cyclin D CDK4 CDK6 Cyclin E CDK 2 • Checkpoint 1 • Cell size? • DNA?
S phase DNA Replication and Protein synthesis Cyclin A CDK 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 Inactive Active
G2 • Checkpoint 2 • All DNA Duplicated? • Cell size? • All DNA Intact? • Repair DNA • Cyclin B
Cell Cycle Regulation M-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. .
Prophase Longest (50 - 60%) • Appearance of chromosomes • Nucleolus disappears • Nuclear membrane breaks down • Centrioles separate and migrate to opposite poles of cell
Metaphase Shortest • 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
Telophase Final 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 The process by which the cytoplasm divides, forming two new cells. • Animals • Cell membrane • pinches inward • Plants • Cell plate
Result of Cell Division Two cells that are identical to each other.