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Unit Goals
• Describe the phases of the cell
cycle.
• Describe the process of Mitosis.
– Describe the functions of mitosis.
• Describe the process of Meiosis.
– Describe the functions of meiosis.
– Explain the consequences of
mistakes.
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Cell Size
• Why not just one large cell?
• Difficult to get nutrients in and
waste out
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Phases of The Cell Cycle
G1,S, and G2
are known
together as
Interphase.
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Interphase
Regular Cells
Somatic cell cycle
• G1 phase- Gap phase, cell
undergoes growth.
• S phase- DNA synthesis
Sex cells
are
called
gametes
• G2 phase- Gap phase. Preparation
for Mitosis. Organelles are
produced.
• M phase- Cell division (Mitosis and
cytokinesis)
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G1 Phase
•Cell Grows
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S Phase
• Chromosomes
Condense
• Chromosomes are
inherited genetic
information
• Chromosomes are
made up of DNA
• Can only be seen
when cells are
dividing
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S Phase
When a cell divides, its two daughter cells must
receive the required number of DNA molecules.
• Chromosomes replicateor copy is made
• The two copies are
•
-attached together at a
point called a centromere.
• -are called sister
chromatid.
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G2 Phase
Organelles must be
replicated (copied)
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M Phase
Two parts:
1.Nuclear division
– Mitosis
2.Cytoplasmic Division
– Cytokinesis
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Mitosis
• Nuclear Division.
• Nucleus divides into two new nuclei Mitosis
keeps the number of chromosomes
constant from one cell generation to the
next.
• In eukaryotes, it is the main process by
which growth and tissue repair is
accomplished.
• Mitosis is also the main process by which
single-celled and many multi-celled
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eukaryotes reproduce asexually.
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4 Steps of Mitosis (PMAT)
• Prophase: Chromosomes condense and attach to
the spindle fibers at their centromere.
• Nuclear
Membrane
breaks down.
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Steps of Mitosis (PMAT)
• Prophase: Centrioles move to opposite sides of
the cell and organize the spindle fibers
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Metaphase:
Chromosomes attach to
spindle fibers
and line up in the middle of
the cell
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Anaphase: Chromosomes separateMove to opposite sides of the cell
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Telophase
• Nuclear Envelope reforms
There
are now
TWO
nuclei in
one cell!
…And they contain
the SAME genetic
information
*SAME NUMBER
OF CHROMOSOMES
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Cytokinesis
• Cytoplasmic division
• Each cell gets half of the
organelles.
• After mitosis: cell pinches
in half to form two new
cells.
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Cytokinesis
• Animal cells
pinch.
• Cytokinesis in
plant cells is
different from
that in animal
cells.
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In plant cells a cell
plate forms from the
•
inside out.
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Results of Mitosis and Cytokinesis
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•Two new cells.
•The new cells- called daughter cells- have
the same number of chromosomes as the
mother cell.
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Results of Mitosis and Cytokinesis
• This occurs in all
somatic cells in
your body.
• You have 46
chromosomes in
all of your
somatic cells-23
pair!
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Mitosis in Onion
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Cells
during
Mitosis
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http://www.youtube.com/watch?v=VlN7K1-9QB0&feature=related
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Concept Map
Cell Cycle
includes
M phase
(Mitosis)
Interphase
is divided into
G1
phase
S
phase
is divided into
G2 phase
Prophase
Metaphase
Anaphase
Telophase
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Meiosis:
Reproduction of Sex Cells
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• Sex cells- Sperm and egg
• Process is called Meiosis
• Similar to Mitosis
Meiosis Introduction Clip
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Meiosis
DIPLOID= 2 copies)
• Cell divides
twice
• First division is
like mitosis and
then the cell
divides again to
create 4 haploid
cells.
Not genetically identical!
Contains ½ (HAPLOID) of the
genetic information.
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31.2
Not genetically identical!
Contains ½ of the genetic
information.
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MEIOSIS=CHROMOSOME REDUCTION DIVISION
Not genetically identical!
Contains ½ of the genetic
information.
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Meiosis
Meiosis Square Dance
• Meiosis is also know as chromosome
reduction division.
• In Humans, starts with 46 and ends
up with 23.
• Why?
• Fertilization creates the diploid
Haploid
condition again
Diploid
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• Sperm formation- 4 haploid
sperm cells are formed.
• Egg formation-most of the
cytoplasm is used in one cell
and the other three
disintegrate.
One
haploid
egg cell
is
formed.
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Meiosis
Video Clip
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Crossing Over
• Sometime during
meiosis the
chromosomes
can exchange
information
• This is called
Crossing Over
• Major source of
genetic diversity
in the species
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Prokaryotic Cells
• Binary fission
• Occurs in Prokaryotic
Cells
• DNA is copied and
then the cell splits in
half.
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Regulation of the
Cell Cycle
• How do cells know
when to divide?
• When to stop dividing?
• Cyclins-proteins that
regulate the cell
cycle.
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Cancer
• Unregulated cell
growth.
• Can form masses of
cells called tumors.
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REVIEW
CLIP
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