Transcript 10 – 2 Cell Division

10 – 2 Cell Division
Mitosis
Chromosomes
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DNA is passed on in
chromosomes
Every organism has a specific #
of chromosomes:
fruit flies 8
humans 46
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Before division called sister
“chromatids”
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Chromatids are attached with a
centromere and become …
Chromosomes are only
visible during cell division
The Cell Cycle
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During the cell cycle, a
cell grows, prepares for
division, and divides to
form 2 daughter cells,
each of which then
begins the cell cycle
again.
1. Interphase = growth
2. Mitosis = division
Events of the Cell Cycle
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Interphase
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centrioles
Period of growth
Hereditary material is in the form of
chromatin
3 stages:
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G1 - “growth”
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Increase in cell size in # of organelles, and
in # of proteins
S – “synthesis”
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nucleolus
DNA replication (chromatin is doubled)
G2 – “growth”
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Continued cell growth
chromatin
Mitosis Begins
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Mitosis is when a
cell divides into two
new cells.
Mitosis is one of the
shortest parts of a
cells life.
However, it has the
most stages.
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Mitosis (1. prophase)
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Mitosis – period of cell
division
4 stages:
Sister chromatid
 Prophase – “prepare”
 Longest phase of mitosis
 Chromatin coils up and
forms chromosomes
 Duplicated chromosmes
are made up of 2
identical sister
chromatids connected at
the centromeres
centromere
Identical
Sister
chromatid
Mitsosis (1. prophase)
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Prophase (continued)
Nucleolus and nuclear membrane
fade away, causing the nucleus to
disappear.
Centrioles move to opposite ends of
the cell
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Centrioles – cylindrical structures made
of microtubles
Spindle fibers form between the
centrioles
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spindle
Spindle – Pulls the sister chromatides
apart.
*the spindle attaches to the
chromosome at the centromere*
centriole
Mitosis (2. Metaphase)
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Metaphase “middle”
 Chromosomes attach
to the spindle fibers
at their centromere
 Chromosomes line
up along the middle
of the cell (equator)
Mitosis (3. Anaphase)
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Anaphase –
“apart”
 Sister
chromatids are
pulled apart by
centrioles.
Mitosis (4. Telophase)
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Telophase – “tear into two”
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Chromatids reach the opposite
sides (pole) of the cell
Chromosomes uncoil or unwind
(chromatin)
Spindle fibers begin to break
down
Nucleolus reappears
New nuclear membrane forms
around each new set of
chromosomes
Plasma membrane begins to
separate into 2 new nuclei
Cytokinesis
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Division of cytoplasm
In animals: “cleavage
furrow” pinches the
plasma membrane to
divide the cytoplasm
In plants: “cell plate”
forms to divide the
cytoplasm
Cell division-again!
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