The Cell Cycle and Mitosis:
“You Complete Me”
A process where one parent cell gives
rise to two daughter cells- exact
replicas of the original cell.
The Cell Cycle
• Every cell goes through a
process of growth, this is called
the cell cycle.
• As one cell enters Mitosis, two
cells exit which are exact
replicas or clones of the
original “parent” cell.
Purpose: to replenish dead or
dying cells, to allow an
organism to grow and develop
Mitosis
• Mitosis occurs in order
for organisms to grow
and develop. In order
to replenish dead or
dying cells such as skin
cells, cells in the
digestive tract and in
the fertilized egg.
• There are 6 main
phases: Interphase,
Prophase, Metaphase,
Anaphase, Telophase &
Cytokinesis.
Interphase
• It may not look like much is going on here, but there is a
lot of activity because the cell must prepare for Mitosis:
protein synthesis, DNA synthesis, replication of other
cellular structures too.
•
• Onion root tip (on left side), whitefish (on right side)
•
Interphase
• 95% of a cell's time is spent in Interphase,
between mitosis periods.
• A copy of DNA is
• made in the
• nucleus
Mitosis: Prophase
• Major processes during
this phase:
• Chromosomes condense
and form visible bodies
• Nuclear envelope breaks
down
•
•
•
Onion root tip (top photo), whitefish (bottom
photo)
Mitosis: Metaphase
• Chromosomes attached
to spindle fibers line up in
the middle (the equator)
of the cell
• Spindle fibers attach to
the centromeres and
other places along the
chromosome
•
•
•
•
Onion root tip (top photo), whitefish (bottom
photo)
Mitosis: Anaphase
• The last bit of DNA at the
centromere replicates to
allow the centromere to
split
• The sister chromatids
separate and are pulled
to opposite sides of the
cell
•
•
•
Onion root tip (top photo), whitefish (bottom
photo)
Mitosis: Telophase
• Chromosomes now
uncoil
• Nuclear envelope
reappears and
surrounds the
chromosomes
•
Onion root tip (top photo), whitefish (bottom photo)
Cytokinesis
The cytoplasm and all its contents are
divided between the 2 daughter cells
(cytoplasmic division)
• The 2 daughter cells
are exact replicas of
the original parent cell
– they are clones
--have the exact same
genetic make-up as the
parent cell.
Can you identify these stages?
A
C
B
D
Summary
• One parent cell begins the journey through the
cell cycle and 2 new identical daughter cells
emerge from one cycle.
• Mitosis occurs regularly in tissues that require
new cells continuously such as skin cells, hair
follicles, the lining of the digestive tract and in a
newly fertilized egg.
• This process is important as it allows for an
organism to grow and develop over its lifespan
and replenishes dead or dying cells in certain
tissues.
Acknowledgements:
• Images taken from the following sites:
– http://biog-101-104.bio.cornell.edu/BioG101_1
04/tutorials/cell_division.html
– http://www.accessexcellence.org/AB/GG/mito
sis2.html
– http://www.biology.arizona.edu/cell_bio/tutorial
s/cell_cycle/cells3.html