Transcript Cell Division and Mitosis

Cell Division and Mitosis
One parent cell giving rise to two
identical daughter cells
What is Mitosis?
Mitosis is the process of
duplication of chromosomes
and division of the nucleus
prior to cell division.
5 Phases of Mitosis
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Includes the time that the cell is not
actively dividing so may last a long time
 The cell carries out its normal life
functions during this phase
 DNA is in the form of chromatin – long
threadlike strands, not visible with light
microscope

Late Interphase

Chromosomes have
replicated.
 Nuclear membrane
is still intact
Nuclei stained blue;
Center and right cell in
interphase
Public Domain:
http://en.wikipedia.org/wiki/File:HeLa_cells_stained_wit
h_Hoechst_33258.jpg
Interphase
= Chromatin
Prophase
Chromatin coils into
chromatids and
become easily visible
with light microscope.
 Duplicate
chromosomes are
attached at the
centromeres.

Fluorescence
microscope image of two
mouse cell nuclei in prophase
(scale bar is 5 µm).
http://en.wikipedia.org/wiki/Prophase
Prophase
In the cell:
Centrioles move to opposite ends of the
cell (animal cells)
 Spindle forms
 Nucleolus disappears
 Nuclear membrane breaks down

Different Forms of Chromosomes
(1) Chromatin during
interphase with
centromere. (2)
Condensed chromatin
during prophase. (Two
copies of the DNA
molecule are now
present) (3) Sister
chromatids from the end
of prophase through
anaphase.
Image modified from http://commons.wikimedia.org/wiki/File:Chromatin_chromosome.png
Prophase

Chromosomal components:
(1) Chromatid
(2) Centromere
(3) Short arm
(4) Long arm
http://en.wikipedia.org/wiki/Centromere
http://en.wikipedia.org/wiki/Prophase
Metaphase
The chromosomes
have aligned along
the equator of the
cell attached to the
spindle fibers by the
centromeres
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Metaphase
http://en.wikipedia.org/wiki/Metaphase
Anaphase
Each centromere splits allowing
identical sister chromatids to
separate and move along the
spindle fibers toward opposite ends
of the cell.
Anaphase

Early Anaphase: The
chromosomes are
starting to migrate
toward opposite poles.

Onion Root Tip
Late Anaphase: The
contraction of the
spindle fibers has
moved the separate
masses of chromatids
farther from the equator.
Whitefish egg
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Anaphase
http://en.wikipedia.org/wiki/Anaphase
Telophase



The chromatids have reached the poles. The
chromatids uncoil back into chromatin.
Each set of chromosomes becomes incorporated in a
new nucleus as the nuclear membrane reforms.
Cytokinesis or cell division now occurs.
http://en.wikipedia.org/wiki/Telophase
Daughter Cells in Interphase
After cytokinesis:


Cells may enter a prolonged period of
interphase when all the processes that
normally take place in the cell occur,
except for cell division.
Cells may repeat the steps of mitosis
and divide again
Phases of Mitosis – Another Look
Public Domain: http://commons.wikimedia.org/wiki/File:Interphase_and_Mitosis.svg
Mitosis in Onion Root Tip
Can you find:
Prophase
Metaphase
Anaphase
Telophase
http://commons.wikimedia.
org/wiki/File:Onion_root_mi
tosis.jpg
http://commons.wikimedia.org/wiki/File:Mitosis_schematic_diagram-en.svg