Cell Cycle
Cell Theory:
* All
living things composed of cells
* Cells are the basic units of structure and function
in living things.
* New cells are produced from existing cells
Nucleus of the Cell:
Controls most cell processes and contains the hereditary
information. This is found as Deoxyribonucleic Acid (DNA)
DNA: Coded instructions for making proteins.
Chromatin: DNA bound to protein – granular and visible in the nucleus.
Chromosomes: Chromatin that condenses in preparation for cell division.
Microtubules:
They aide in cell division, separating chromosomes
(known as centrioles in animal cells).
PROKARYOTE CELL
DIVISION
Cell Division called Binary Fission
Asexual Reproduction
DNA = One Circular Chromosome
and Plasmids
EUKARYOTE CELL
DIVISION
Cell Division called the Cell Cycle
Growth and replacement
of old and/or dying
cells
DNA = 10-50 chromosomes per cell
Humans = 46 (23 identical pairs)
Cell Cycle:
Phase 1: Interphase
G1 - primary growth phase
S – synthesis; DNA replicated
G2 - secondary growth phase
Phase 2: Mitosis
Phase 3: Cytokinesis
Phase 1: Interphase
G1 - primary growth phase
Cell Matures:
Growth and Organelles
S – synthesis; DNA replicated
DNA copied/replicated
G2 - secondary growth phase
Cell Structures needed for division made
Centrioles



Chromatin condenses into chromosomes
Mitotic spindle forms and attaches to
centromeres
Nuclear membrane/nucleolus broken down.
Centrioles
dissolving

Chromosomes line up at the equator of the cell
Centriole
Equator
Centromere
Centriole

Sister Chromatids pulled apart to opposite
poles of the cell.
Equator




Sister Chromatids completely at opposite poles
Nuclear envelope forms
Nucleolus appears
Cytokinesis occurs
Equator
Phase 3: Cytokinesis
Division of cell into two –
Division of the cytoplasm by a cleavage
furrow
Cleavage
Furrow
Draw and Label the Following:
• Interphase
• Nuclear Membrane
• Chromatin
• Prophase
• Centrioles
• Nuclear Membrane
(disappearing)
• Chromosomes
• Metaphase
• Centrioles
• Chromosomes
• Mitotic spindle
• Anaphase
• Centrioles
• Chromosomes
• Mitotic spindle
• Telophase/Cytokinesis
• Chromosomes returning
to chromatin
• Nuclear Envelope forming
• Cleavage Furrow
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Early Anaphase
Early prophase
Metaphase
Interphase
Late Prophase
Late telophase,
Advanced cytokinesis
Early Telophase,
Begin cytokinesis
Mid-Prophase
Late
Anaphase
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
http://www.youtube.
com/watch?v=ZEwdd
r9ho4&feature=related
Karyotype
 A picture of the
chromosomes from a
human cell arranged
in pairs by size



First 22 pairs are
called autosomes
Last pair are the sex
chromosomes
XX female or XY
male
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The Y Chromosome Decides
Y - Chromosome
X - Chromosome
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(Eggs and Sperm)
Males:
Spermatogenesis (formation of sperm)
Females:
Oogenesis (formation of eggs)
Two Stages: Meiosis I and Meiosis II
During Meiosis I – Homologs form Tetrads and crossing over occurs,
all resulting cells are still diploid (2N) 46 chromosomes
During Meiosis II – Chromosomes are split and all cells become
haploid (1N) 23 chromosomes
Entire process called reduction division
Why is this important?
Homologous chromosomes
(compare to sister
chromatids)
Join to form a
tetrad
Called Synapsis
(compare to a centromere)
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


Homologous
chromosomes in
a tetrad cross
over each other
Pieces of
chromosomes or
genes are
exchanged
Produces
Genetic
recombination in
the offspring
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Crossing-over multiplies the already huge
number of different gamete types
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Lets compare Mitosis and Meiosis –
What do you know?
46 chromatids
(92 chromosomes,
paired after
replication –
held by a
synapsis/centro
mere)
46 chromosomes
each side
Mitosis:
46 chromosomes
Meiosis:
23 chromosomes
Mitosis
Meiosis
2
Number of
divisions
1
Number of
daughter cells
2
4
Yes
No
Same as parent
Half of parent
Where
Somatic cells
Germ cells
When
Throughout life
At sexual maturity
Growth and
repair
Sexual reproduction
Genetically
identical?
Chromosome #
Role
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