Download Mitosis

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Why do cells divide?
• Growth and
Repair
• Creation of
gametes
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Chromosomes
Made of densely packed DNA
Human Eukaryotic Cells
1.Somatic (body) cells
A.46 chromosomes
b.Diploid
2.Sex cells (gametes)
a.23 chromosomes
b.Haploid
Why would sex cells need half
the number of chromosomes ?
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Karyotype
An organized profile of persons
chromosomes
Homologous
Chromosomes
--Chromosome pairs
that carry genes for
the SAME trait
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Phases of The Cell Cycle
G1,S, and G2
are known
together as
Interphase.
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Interphase
Body Cells
Somatic cell cycle
• G1 phase- Gap phase, cell
undergoes growth.
• S phase- DNA synthesis
(replication)
Sex cells
are
called
gametes
• G2 phase- Gap phase. Preparation
for Mitosis. Organelles are
produced.
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Mitosis
• Nuclear Division.
• Nucleus divides once into two identical
nuclei with the same DNA
• YEILD: 2 diploid somatic cells
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Meiosis
• Nuclear Division.
• Nucleus divides twice into four =nuclei
with different DNA
• YEILD: 4 haploid gametes
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Mitosis
Meiosis
1.Which type of cells go
through Mitosis?
5.Which type of cells go
through Meiosis?
2.The nucleus divides into
how many nuclei?
6.How many times does the
nucleus divide?
3.Is the DNA the same or
different?
7.Is the DNA the same or
different?
4.What does mitosis yield ( or 8.What does meiosis yield (
make) ?
or make)?
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Mitosis
Meiosis
1.Which type of cells go
through Mitosis?
Somatic ( Body)
5.Which type of cells go
through Meiosis?
Gametes (Sex)
2.The nucleus divides into
how many nuclei?
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6.How many times does the
nucleus divide?
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3.Is the DNA the same or
different?
same
7.Is the DNA the same or
different?
different
4.What does mitosis yield ( or 8.What does meiosis yield (
make) ?
or make)?
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2 identical diploid somatic 4 different haploid gametes
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4 Steps of Mitosis (PMAT)
Prophase:
Chromosomes condense
Nuclear membrane breaks down.
Centrioles move to opposite sides of the cells
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Metaphase:
-Chromosomes attach to
spindle fibers
-Chromosomes line up in the
middle of the cell
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Anaphase:
-Chromosomes separate
-Chromosomes move 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.
• cell pinches in
half to form
two new cells.
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In plant cells a cell plate forms from
the inside out.
•
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Mitosis in Onion
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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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Cytokinesis
• Animal cells
pinch.
• Cytokinesis in
plant cells is
different from
that in animal
cells.
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Cell Size
• Why not just one large cell?
• Difficult to get nutrients in and
waste out
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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
• Chromosomes
replicate-or 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 review
video clip with
quiz!
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Results of Mitosis and Cytokinesis
• Two new cells.
• The new cells- called daughter
cells- have the same number of
chromosomes as the mother cell.
• 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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Cells
during
Mitosis
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Reproduction of Sex
Cells
• Sex cells- Sperm and egg
• Process is called Meiosis
• Similar to Mitosis
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Meiosis
• Cell divides twice
• First division is like
mitosis and then the cell
divides again to create 4
haploid cells.
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MEIOSIS=CHROMOSOME REDUCTION DIVISION
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Meiosis
• Meiosis is also know as chromosome
reduction division.
• Start with 46 and ends up with 23.
• Why?
• Fertilization creates the diploid
condition again
Haploid
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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