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Cell Division
Division of the Cell
Chapter 10
When a living thing grows, what
happens to its cells?
Does an animal get larger because
its cells increase in size or because it
produces more of them?
When a cell divides it forms two identical
“daughter cells”. The process by which a cell
divides into two new daughter cells is called
cell division.
Division of the Cell
Page 244
Some eukaryotic cells divide for growth,
development, and repair of the organism…but
not all somatic cells undergo mitosis and those
that do, do so at different rates (see page 249 in
your text).
Skin cells continuously undergo mitosis and
divide, so that our skin is constantly renewed and
repaired.
Heart cells and many nerve cells stop undergoing
mitosis soon after birth. (Caution:
overconsumption of alcohol can kill nerve/brain
cells, and it is believed that most can never be
replaced; they will never “grow back.”).
Liver cells are somewhere in between. In a
healthy adult, liver cells normally do not
divide. Where there is minor liver damage
liver cells can and do divide to repair the
damage. Major liver damage or advanced
cirrhosis is too much damage to be repaired
through mitosis.
It is though, possible to use one adult liver to
do liver transplants for four babies, and if all
goes well, these pieces will eventually
regenerate whole livers.
Ratio of surface area to volume
(Page 243)
Cell Cycle
http://stevebambas.com/images/03_30CellCycle-L.jpg
Division of the Cell
Before cell division occurs, the cell replicates
or copies its entire DNA. DNA replication
occurs during the S phase of Interphase.
Each daughter cell gets one complete set of
genetic information. This division of the
genetic material is called mitosis.
Mitosis
• http://www.youtube.com/watch?v=VlN7K19QB0
Mitosis
Mitosis has four phases:
• Prophase
• Metaphase
• Anaphase
• Telophase
Prophase
-First and longest phase of
mitosis.
During prophase:
• the chromatin
condenses into
chromosomes,
• the centrioles separate
and spindles begin to
form, and
• the nuclear envelope
breaks down.
http://a248.e.akamai.net/7/248/430/2008
0327144033/www.mercksource.com/ppd
ocs/us/common/dorlands/dorland/image
s/mitosis(1).jpg
Metaphase
-Second phase of mitosis.
During metaphase:
• the chromosomes line
up across the center of
the cell, and
• each chromosome is
connected to a spindle
fiber at its centromere.
http://a248.e.akamai.net/7/248/430/2008
0327144033/www.mercksource.com/ppd
ocs/us/common/dorlands/dorland/image
s/mitosis(1).jpg
Anaphase
-Third phase of mitosis.
During anaphase:
• the chomosomes
separate into individual
chromatids and are
moved apart to each end
of the cell.
http://a248.e.akamai.net/7/248/430/2008
0327144033/www.mercksource.com/ppd
ocs/us/common/dorlands/dorland/image
s/mitosis(1).jpg
Telophase
-Fourth and final phase of mitosis.
During telophase:
• the chromatids gather at opposite ends of the
cell and become less distinct, and
• two new nuclear envelopes begin to form.
http://a248.e.akamai.net/7/248/430/20080327144033/www.mercksource.com/ppdocs/us/common/dorlands/dorland/image
s/mitosis(1).jpg
Cytokinesis
The nucleus has divided, mitosis is over and all
that now remains to complete cell division is
the division of the cell itself, a phase called
cytokinesis. This phase occurs after telophase
and is not part of mitosis. (Mitosis involves the
division of the chromosomes in the nucleus.)
Cytokinesis takes place in different ways,
depending on whether the cell is an animal
cell or a plant cell.
Cytokinesis
In plant cells, a structure known as the cell
plate forms midway between the divided
nuclei. This cell plate gradually develops into a
membrane, separating the two daughter cells.
A cell wall then begins to develop.
Cell Plate
http://www.vcbio.science.ru.nl/images/cellcycle/mito_bellevalia_cytokinesis.jpg
Cytokinesis
In animal cells, the cell membrane is drawn
inward until the cytoplasm is pinched into two
nearly equal parts.
In both animal and plant cells, each identical
daughter cell contains its own nucleus and
cytoplasmic organelles.
http://a248.e.akamai.net/7/248/430/20080327144033/www.mercksource.com/ppdocs/us/common/dorlands/dorland/image
s/mitosis(1).jpg
Mitosis Review
• http://vimeo.com/8333643