Transcript Mitosis

Mitosis & Cytokinesis
Chapter 10
Mitosis
Mitosis
Cell Division
In eukaryotes, cell division occurs in two
major stages.
 The first stage, division of the cell nucleus, is
called mitosis.
 The second stage, division of the cell
cytoplasm, is called cytokinesis.
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Why do cells divide by
Mitosis?
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Growth of the
organism
Repair of tissue
damage
Replacement of
old cells
Reproduction of
some single celled
organisms (Which
ones?)
Amobea
Reproducing
Which single celled organisms
reproduce by mitosis?
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The protists or member of the
kingdom Protista
They are eukaryotic cells & have a
nucleus. Mitosis = division of
nucleus.
Bacteria DO NOT divide by mitosis
because they don’t have a nucleus.
Bacteria reproduce via binary fission
Cells produced by Mitosis…….
Skin
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Are called
daughter cells.
Are identical to
the original cell
Are identical to
each other
Have the same #
of chromosomes
Have an identical
chromosome
makeup
A Duplicated Chromosome
centromere
one chromatid
its sister
chromatid
One chromosome in the duplicated state
Diploid vs. Haploid Cells
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Diploid=
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A cell that has 2 sets of chromosomes
One set came from each parent (mom
and dad)
Chromosomes come in pairs
Humans have 23 pairs of
chromosomes for a total of 46
chromosomes per cell
Somatic Cells are body cells (all
except sperm and egg) and are
diploid
Diploid vs. Haploid Cells
 Haploid
=
A cell with 1 set of chromosomes
 Gametes or sperm or egg are
haploid.
 In humans, gametes contain 23
chromosomes
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Stages of Mitotic Cell Division
 Prophase
= “1st”
 Metaphase = “middle”
 Anaphase = “apart”
 Telophase = “far or
separate”
Interphase
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“Intermission”
Normal metabolic
(cell) activities
Major state of the
cell cycle.
Cell spends 90% of
time here
DNA is in the form of
chromatin, not
coiled into
chromosomes
The nucleus appears
solid. A nucleolus
can sometimes be
seen.
Late Interphase
The cell prepares
for mitosis
 DNA doubles
(replicates) and
forms sister
chromatids
 Centrioles
double in animal
cells
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Prophase
 Nuclear
membrane
disappears
 Replicated
DNA is
condensed
 Chromosomes
form and can
be seen
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Spindle fibers
start to form
Metaphase
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Chromosomes
line up at that
equator or
middle of the
cell
The ends of
the
chromosomes
point toward
the ends or
the poles of
the cell.
Spindle & spindle fibers: Pull
apart the sister chromatids
Spindle
fibers
Anaphase
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Chromosomes
move to opposite
poles
Centrioles are at
the poles in
animals
Spindle apparatus
is at the pole in a
plant
Telophase
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Chromosomes
gather at opposite
ends of the cell and
lose their distinct
shape.
Cell plate or new
cells membranes
form
Nucleus
reappears
Cytokinesis:
cytoplasm divides & splits apart
Return to Interphase
New daughter cells each
resume the cell cycle in G1 of
interphase.
 They will each have a period of
growth and normal cell activity
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before they each divide.
Cytokinesis
Mitosis is over, and
the spindle is now
disassembling.
Band of microfilaments at the
former spindle equator contracts.
The contractions
continue and cut
the cell in two.
Cytokinesis in Plants
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Cell plate
In plants, a structure known as the cell
plate forms midway between the divided
nuclei.
Cell wall
Stages of Mitosis
Plant versus Animal Mitosis
Plant:
 Cell wall from
cell plate in
telophase
 Spindle
apparatus
Animal:
 No cell wall
 Cell
membrane
cytokinesis
 Centrioles
Cancerous cells……...
1.Divide too many
times
2.Divide into more
than two cells!
 Masses of cells =
 “tumors”
 benign
 malignant