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Cell Division and Mitosis
Chapter 10
Cancer and the Cell Cycle
Cell Division Results in Genetically Identical Daughter Cells
Chromosome duplication (including DNA synthesis)
0.5 !m
Centromere
Sister chromatids
Separation of sister
chromatids
Centromeres Sister chromatids
Each Chromosome has a Homologue
The Cell Cycle
G1
G2
S (DNA synthesis)
INTERPHASE Prop
hase
M
etap
hase
Mitosis (M phase)
G1 Period of cell growth before the DNA replicates
S Period when DNA Replicates and chromosomal proteins are duplicated
Cytokinesis
G0 Cell cycle arrest
G2 Period after DNA replicates; cell prepares for division (In
terp
hase
end
s in
par
ent c
ell)
Phases of the Cell Cycle
G2 OF INTERPHASE PROPHASE PROMETAPHASE
Phases of the Cell Cycle, cont.
The Mitotic Spindle
Microtubules Chromosomes
Sister chromatids
Aster Centrosome
Metaphase plate
Kineto- chores
Kinetochore microtubules
0.5 !m
Overlapping nonkinetochore microtubules
1 !m Centrosome
Prometaphase Chromosome
Sister chromatid II
Sister chromatid I
Kinetochore I
Spindle pole
Kinetochore II
Spindle microtubules
Spindle pole
A cell at interphase: Cytoplasm
Nucleus
Prophase Cytokinesis Telophase
Anaphase Prometaphase Metaphase
Anaphase detail Spindle pole
Microtubules assembled into a spiral
Spindle midpoint Chromosomes
Spindle pole
Cytokinesis in Animal Cells: Cleavage Furrow
Cytokinesis in Plant Cells by Cell Plate Formation
Vesicle Cell wall
1 A layer of vesicles Containing wall material collects in the plane of the former spindle midpoint (arrow).
2 More vesicles are added to the layer until it extends across the cell.
3 The vesicles fuse together, dumping their contents into a gradually expanding wall between the daughter cells.
4 Vesicle fusion continues until the Daughter cells are separated by a continuous new wall, the cell plate.
Mitosis in Onion Root Tip
The Cell Cycle Control System
G1 checkpoint
G1 S
M
M checkpoint G2 checkpoint
G2
Control system
G1
G1 checkpoint
G1
G0
If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle.
If a cell does not receive a go-ahead signal at the G1 checkpoint, the cell exits the cell cycle and goes into G0, a nondividing state.
Cell Cycle Regulation: Cyclin/CDK Control
Cyclin B Cyclin B
CDK1
CDK1
Cyclin E
Cyclin E
CDK2
CDK2
G2-to-M checkpoint
G1-to-S checkpoint
G1
M G2
S
Cyclin B is degraded
Cyclin E is degraded
Cell Cycle Regulation: Cyclin/CDK Control
CDK1
G1 G2 S M S M G2 G1 M
Cyclin B
Time Fluctuation of CDK1 activity and cyclin concentration during the cell cycle
Rel
ativ
e co
ncen
trat
ion
The CDK/cyclin complex is also called MPF (mitosis-promoting factor)
Growth Factors Trigger Intracellular Signaling Systems
PDGF
Growth factors can override cellular controls that otherwise inhibit cell division
Platelet-derived growth factor (PDGF) receptor is a receptor tyrosine kinase (RTK) that initiates a MAP kinase cascade to stimulate cell division
Growth Factor Receptors and Tumor Suppressors
Normal Cell • Growth factor present • Normal receptor • Cell division regulated at G1
Cell with one mutation • No growth factor present • Mutated receptor • G1 checkpoint overridden
Cell with two mutations • No growth factor present • Mutated receptor and mutated tumor suppressor
Normal tumor suppressor repairs damaged DNA
Mutant tumor suppressor Does not repair damaged DNA
Benign tumor Malignant tumor
Internal and External Signals at the Checkpoints
Cells anchor to dish surface and divide (anchorage dependence).
When cells have formed a complete single layer, they stop dividing (density-dependent inhibition).
If some cells are scraped away, the remaining cells divide to fill the gap and then stop (density-dependent inhibition).
25 !m Normal mammalian cells
Cancer Cells ignore Internal and External Signals at the Checkpoints
Cancer cells do not exhibit anchorage dependence or density-dependent inhibition.
Cancer cells 25 !m
Tumor Suppressors and Proto-oncogenes Influence the Cell Cycle Tumor Cells
Fig. 10-16, p. 215
Facial Tumor Loss of Cell Cycle Controls in Cancer Cells
! Cancer cells do not respond normally to the body’s control mechanisms
! Cancer cells form tumors, masses of abnormal cells within otherwise normal tissue
! If abnormal cells remain at the original site, the lump is called a benign tumor
! Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form secondary tumors
Breast Cancer Development
Cancer cell
Blood vessel
Lymph vessel Tumor
Glandular tissue
Metastatic tumor
A tumor grows from a single cancer cell.
Cancer cells invade neighboring tissue.
Cancer cells spread through lymph and blood vessels to other parts of the body.
A small percentage of cancer cells may survive and establish a new tumor in another part of the body.
Bacterial Cell Division Bacterial chromosome Cell wall
Plasma membrane
Origin of replication (ori)
Replication origins
1 A bacterial cell before its DNA replicates.
2 Replication begins and ori and proceeds in opposite directions. replication takes place in the middle of the cell where the DNA replication enzymes are located. 3 The two replicated origins migrate to the poles of the cell while replication continues.
4 Replication is complete. Cell division begins as the plasma grows inward, and a new cell wall is synthesized.
5 Binary fission produces two daughter cells.
Unreplicated region of chromosome
Replicated chromosomes