Download Mitosis vs. Meiosis

MITOSIS VS. MEIOSIS
Body Cell Division
MITOSIS
AND
MEIOSIS
• Mitosis:
-division of somatic (body) cells
• Meiosis
-division of gametes (sex cells)
I. STEPS OF
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MITOSIS
Interphase
Prophase
Metaphase
Anaphase
Telophase (& cytokenesis)
II. INTERPHASE
• Cell goes
through its
regular
functions
• Visible nucleus,
nuclear
envelope and
nucleolus
III. PROPHASE
• DNA inside the
cell condenses
and makes visible
chromosomes
• Nucleus begins to
disappear
• Spindle fibers
begin to form
IV. METAPHASE
• Chromosomes line
up along the
center (equator)
of the cell
• This step is
“quality control”
and makes sure
each chromosome
divides equally
V. ANAPHASE
• Chromosomes
split apart to
become sister
chromatids
• Sister
chromatids
move to
opposite sides
of the cell
VI. TELOPHASE
• Chromosomes
arrive at separate
ends of the cell
• Chromosomes relax
and begin to uncoil
• Nuclear membrane
begins to reform
• Spindle fibers
disappear
CYTOKINESIS
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Animal Cell
Plant Cell
The division of
the cell
cytoplasm that
usually follows
mitotic or
meiotic
division of the
nucleus.
General Definitions
•
Diploid – normal number of chromosomes
in a body cell after mitosis (2n)
o
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Example: Humans have 46 chromosomes in
each body cell
Haploid – half the normal number of
chromosomes after meiosis (n)
o
Example: Human sex cells (sperm and egg)
have 23 chromosomes
Meiosis Big Ideas
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Meiosis makes sex cells or gametes
In meiosis, cell division happens twice and
forms four cells with half the genetic material
Meiosis reduces the number of chromosomes to
half of the original number of chromosomes
Meiosis provides genetic variation because all
of the sex cells produced at the end have
different genetic information
Interphase
•
•
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Cell goes through its
regular functions
DNA copies
DNA is in the form of
chromatin
Prophase I
• Chromatin (DNA)
organizes to form visible
chromosomes
• Nuclear membrane
breaks down
• Spindle fibers start to
form
• Crossing over occurs
Crossing Over (Prophase I)
Crossing over – exchange of DNA from
one homologous chromosome to another
• It is responsible for genetic variation
• After crossing over, no two sister
chromatids are alike
•
Metaphase I
• Homologous
Chromosomes line up at
the equator (middle) of
the cell
• Spindle fibers attach to
the centromere of each
chromosome
Anaphase I
• Homologous
chromosomes move to
the poles of the cell
Telophase I
• Cells divide for the first time
• Cytokenesis separates the
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cytoplasm of each cell
Two new cells are formed –
they are NOT genetically
identical
Nuclear membrane reforms
Chromosomes relax to form
chromatin
Spindle fibers disappear
Prophase II
• Chromatin (DNA)
organizes to form visible
chromosomes
• Spindle fibers begin to
form
• Nuclear membrane
breaks down
Metaphase II
• Chromosomes line up
along the equator
(middle) of the cell
• Spindle fibers attach to
the centromere of each
chromosome
Anaphase II
• Sister chromatids are
pulled apart
• Chromosomes are pulled
to the poles of each cell
Telophase II
• Cells divide
• Cytokinesis fully
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separates the cytoplasm
of each cell
Nuclear membrane
reforms
Chromosomes relax
Spindle fibers disappear
Four genetically different
sex cells (gametes) are
Why do sex cells have HALF the
chromosome number?
Study Tools
•
P. 275
www.cellsalive.com
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Mitosis (body cell division) animation
Meiosis (sex cell production) animation
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Link:
http://www.cellsalive.com/meiosis.htm