Cell Division
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
Cyclins/Kinases Complexes
G1 phase
Cellular Growth and Development
Cyclin D
CDK4
CDK6
Cyclin E
CDK 2
Checkpoint 1
•Cell size?
•DNA?
Cyclin D
cyclin D-dependent kinase Cdk6
S phase
DNA Replication and Protein synthesis
Cyclin A
CDK 2
Cyclin A
• Residues 173432
• 2 similar
domains
• Cyclin fold
–5 α-helices
CDK 2
• Domain 1
–85 residues
–1 α-helix
–5 stranded βsheet
• Domain 2
–213 residues
–α-helices
Cyclin A/CDK 2 Complex
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.
Chromosomes
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
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.