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Transcript 
Cell Cycle and Mitosis
9.1 Cell Cycle
What is the cell cycle?



Repeating series of events
Five stages
Interphase (3 parts)




G1
S
G2
M phase (2 parts)


Mitosis
Cytokinesis
What happens in Interphase?

G1



S


Normal growth
Recovery from last
mitotic division
Replication of
chromatids
G2

Synthesis of proteins for
mitosis
Cell Cycle and Mitosis
9.2 M phase: Mitosis and cytokinesis
What happens during the M phase?

Mitosis


Prokaryotes undergo
binary fission instead
Cytokinesis
What is a chromosome?


Length of DNA with
genes and noncoding
regions
Highly condensed
version of chromatin

Heterochromatin vs.
euchromatin
What is mitosis?


Division of nuclear
material
Duplicated chromosomes
are split


This creates unduplicated
chromosomes
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
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?

Cytokinesis


Animal cells


Cytoplasmic division
Contractile ring
Plant cells

Cell plate
Cell Cycle and Mitosis
9.3 Cell cycle control and cancer
Why do cells undergo mitosis?

Repair and replacement

Apoptosis of somatic cells


blebbing
Stem cells

Serve as reservoir for replacing old cells
What controls the cell cycle?

Checkpoints

G1



Apoptosis if DNA is
damaged
G2
M
What is cancer?


Uncontrolled cell growth
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
Mutations of
either/both

Proto-oncogenes


Become oncogenes
Tumor suppressor
cells
What are proto-oncogenes?



“gas pedal” of cell
division
Mutated oncogene
Examples



ras genes
rasN (leukemia)
BRCA1
What are tumor suppressor genes?



Brake pedal of cell
division
If mutated  loss of
cell cycle control
Examples


p53 gene
RB gene
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