Cell Cycle and Mitosis
9.1 Cell Cycle

What is the cell cycle?
 Repeating series of events
 Five stages
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Interphase (3 parts)
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G
1
S
 G
2
M phase (2 parts)
Mitosis
Cytokinesis

What happens in Interphase?
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G
1
Normal growth
Recovery from last mitotic division
 S
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 Replication of chromatids
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G
2
Synthesis of proteins for mitosis

Cell Cycle and Mitosis
9.2 M phase: Mitosis and cytokinesis

What happens during the M phase?
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Mitosis
Prokaryotes undergo binary fission instead
 Cytokinesis

What is a chromosome?
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Length of DNA with genes and noncoding regions
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Highly condensed version of chromatin
Heterochromatin vs. euchromatin

What is mitosis?
 Division of nuclear material
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Duplicated chromosomes are split
This creates unduplicated chromosomes
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Chromosome terminology
Sister chromatids
Kinetechore
Centromere
Diploid (2n) vs. haploid (1n)

What are the stages of mitosis?
 Prophase
 Prometphase
 Metaphase
 Anaphase
 Telophase

What happens in prophase?
 Nuclear envelope disappears
 Centrioles move apart
 Nucleous disappears
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Chromatin condenses to form chromosomes
Recall that these are duplicated

What happens during prometaphase?
 Kinetechores appear
 Spindles attach
 Polar spindle fibers extend and overlap

What happens during metaphase?
 Duplicated chromosomes align along metaphase plate

What happens during anaphase?
 Sister chromatids pulled apart
 Chromosomes are now unduplicated

What happens during telophase?
 Reverse of prophase
 Cleavage furrow develops in animal cells

What is the second part of the M phase?
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Cytokinesis
Cytoplasmic division
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Animal cells
Contractile ring
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Plant cells
Cell plate

Cell Cycle and Mitosis
9.3 Cell cycle control and cancer

Why do cells undergo mitosis?
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Repair and replacement
Apoptosis of somatic cells
 blebbing
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Stem cells
Serve as reservoir for replacing old cells

What controls the cell cycle?
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Checkpoints
G
1
 Apoptosis if DNA is damaged
G
2
M

What is cancer?
 Uncontrolled cell growth
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Characteristics
Neoplasms (tumors)
Benign vs. malignant
Angiogenesis
Metastasis
Abnormal nuclei
Undifferentiated (anaplasia)
Lack contact inhibition
No apoptosis

How does cancer occur?
 Mutations of cell repair genes
 Activation of telomerase

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Mutations of either/both
Proto-oncogenes
 Become oncogenes
Tumor suppressor cells

What are proto-oncogenes?
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“gas pedal” of cell division
Mutated  oncogene

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Examples ras genes rasN (leukemia)
BRCA1

What are tumor suppressor genes?
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Brake pedal of cell division
If mutated  loss of cell cycle control
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Examples p53 gene
RB gene