CELL GROWTH

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Dr. Michael C. Potter Paul VI Catholic High
School 2006
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• CHROMOSOME ANATOMY
• A. Chemistry
• 1. DNA (40)
• One continuous Strand of DNA
• Each (human) approx. 5.0 cm.
• Contains 140,000,000 nucleotides
• 2. PROTEIN (60)
• a. Histone Protein
• b. Scaffolding Protein

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2. PROTEIN a. Histone Proteins Forms
octad (8 proteins) Positively charged
Promotes DNA coiling Forms NUCLEOSOME b.
Scaffolding Proteins Backbone of DNA
coiling
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2. PROTEIN c. Cohesin Integral part of
Centromere Responsible for binding sister
chromatids together d. Condensin Joins
loops of coiled DNA Aids in condensing chromosome
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CONDENSIN
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SUPER COIL
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B. STRUCTURE 1. Centromere Constriction
on chromosome Variable placement on
specific chromosomes Complex structure
joins 2. Sister Chromatids Replicated
chromosome Contains identical genes
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B. STRUCTURE 3. Homologous Chromosomes
Contains similar genes for same traits One
from each parent Alleles different genes for
same trait on homologues
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B. STRUCTURE 4. Heterochromatin Highly
condensed portions of chromatin Unable to
be read 5. Euchromatin Condensed only
in cell division Allows expression of
DNA 6. Karyotype Array of chromosomes of
an individual (human 46)
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B. STRUCTURE 6. Karyotype a. Diploid
(2n) Represents the two sets of homologous
chromosomes in a somatic cell b. Haploid
(n) Represents one set of chromosomes (i.e.
from one parent) in a somatic cell.
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Sister Chromatid
?
?
Homologous Chromosomes
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II. CELL CYCLE A. INTERPHASE 1. G1
Primary Growth Phase- Major portion of
cell life span Synthesize RNA Protein
Centriole duplicated (animal) 2. S1 Cell
Synthesis Phase- DNA Replicated
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A. INTERPHASE 3. G2 Secondary Growth
Phase- Organelles Replicate
Chromosomes Condense Microtubules begin
assembly Centrioles enlarge but remain
in single centrosome
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B. MITOSIS (M Phase) 1. Prophase
Chromosome condensation Spindle apparatus
assembled Nuclear envelope breaks down
E.R. absorbs Golgi dissembles
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B. MITOSIS 1. Prophase Microtubule
Assembly completed Kinetochore
Microtubules Astral Microtubules Polar
Microtubules
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B. MITOSIS 2. Metaphase (Division of
centromere) Alignment of chromosomes
Kinetochore attachment Centromeres Divide
Metaphase Plate
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B. MITOSIS 3. Anaphase Shortest of
the phases Sister chromatids pulled apart
Centromeres move to poles 4. Telophase
Spindle disassembled Nuclear envelope
re-forms Gene expression commences
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B. MITOSIS 3. Anaphase Shortest of
the phases Sister chromatids pulled apart
Centromeres move to poles 4. Telophase
Spindle disassembled Nuclear envelope
re-forms Gene expression commences
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C. CYTOKINESIS Cytoplasmic division 1. Animal
Cells Constriction furrow (actin) Furrow
deepens to division 2. Plant Cells Cell Plate
forms Primary cell wall of cellulose Secondary
cell wall of lignin Middle lamella of pectin
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C. CYTOKINESIS 3. Fungi/Protists
Mitosis occurs in intact nucleus Nuclear
division occurs after mitosis is
complete Organelle replication is not equally
distributed to daughter cells
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III. CELL CYCLE CONTROL A. Extracellular
Controls 1. Growth Factors 2. Mitogens 3.
Survival Factors B. Intracellular
Controls 1. Checkpoints 2. Cyclin Dependent
Kinases (Cdks)
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• Extracellular Controls
• 1. Mitogens Stimulate cell division by
• relieving negative controls that block
• process through the cycle
• Release the brake on Cdk activity
• Function primarily in the G1 Stage
• Responds to signals for cell proliferation
• Examples
• PDGF (Platelet Derived Growth Factor)
• EGF (Epidermal Growth Factor)

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• Extracellular Controls
• 2. Growth Factors Bind to receptors on
• the cell membrane surface and activate
• intracellular signaling.
• 3. Survival Factors Signals from other
• cells preventing the cell from entering
• apoptosis.
• Competition for survival factors-those
• having enough survive

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B. Intracellular Controls 1. Checkpoints
Specific sites in the cycle that monitor the
progress of cell division. Types are a.
Unreplicated DNA Checkpoint b. Spindle
Assembly Checkpoint c. Chromosome Segregation
Checkpoint d. DNA Damage Checkpoint
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B. Intracellular Controls 1. Checkpoints
Three principal sites for checkpoint activity
in the cycle a. G1 Checkpoint Restriction
Point in animal cells, Start in yeast
cell. Assesses environmental conditions b.
G2 Checkpoint Triggers start of M Phase c.
M Checkpoint Assesses mitosis
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B. Intracellular Controls 2. Cyclin
Dependent Kinases (Cdks) Proteins that activate
or suppress activity in the cell
cycle Inactive until bound to a CYCLIN Express
their activity at the various
checkpoints a. Cyclins Proteins that
undergo synthesis degradation in each cell
cycle
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• Checkpoints
• a. G1 Checkpoint
• Restriction Point in animal cells
• Multiple control factors present
• Requires interaction of Cyclin
• G1 Cdk to pass through
• Rb Protein (Retinoblastoma)
• P53 Protein influential here

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• Checkpoints
• a. G1 Checkpoint
• Rb Protein Blocks progression into
• S Phase
• Influenced by environment factors
• Mitogens
• Growth Factors
• Functions as a dam in a stream

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• Checkpoints
• a. G1 Checkpoint
• P53 Gene Guardian Angel gene
• Assesses DNA
• Prevents passage into S Phase if
• DNA inaccurate
• Allows time for repair correction
• If severe damage ? apoptosis
• Better dead than read

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• Checkpoints
• b. G2 Checkpoint
• Occurs after S Phase
• Requires completion of DNA synth.
• Ensures DNA replicated only ONCE
• Controlled by a variety of Cdks and
• proteins
• Affects the Replication Origin of
• DNA

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