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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 somatic 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 cell divides 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 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 they
can never be replaced; that 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.
Cell Growth (p. 341)
Cells that do divide, grow larger.
They cannot just keep growing indefinitely
because the larger the cell,
- the more demands are placed on its DNA
- the more trouble it has moving enough
nutrients and wastes across the cell
membrane.
Ratio of surface area to volume
(Page 243)
Division of the Cell
Remember that before cell division occurs, the
cell replicates or copies its entire DNA. DNA
replication occurs during a phase in the cell
cycle called Interphase.
Each daughter cell gets one complete set of
genetic information. This division of the
genetic material is called mitosis.
Cell Cycle
http://stevebambas.com/images/03_30CellCycle-L.jpg
The cell cycle has 6 phases:
•
•
•
•
•
•
Interphase (which has 3 subphases: G1, S, G2)
Prophase
}
Metaphase
} All 4 are phases of mitosis
Anaphase
}
Telophase
}
Cytokinesis
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 a spindle begins 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
The 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
The third phase of
mitosis.
During anaphase, the
sister chromatids
separate into individual
chromosomes and are
moved apart.
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
The fourth and final phase of mitosis.
During telophase:
• the chromosomes 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
All that now remains to complete cell division
is the division of the cytoplasm itself, a phase
called cytokinesis. This phase occurs after
telophase.
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 in this
membrane.
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
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 in this
membrane.
Cell Plate
http://www.vcbio.science.ru.nl/images/cellcycle/mito_bellevalia_cytokinesis.jpg
Summary
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Stage of
mitosis
1
2
3
4
Immediately
following
mitosis
Number of
cells
1
1
1
1
2
Nuclear
envelope
Breaking
down
None
None
Reforming
Established
Sister
chromatids
Together
Together
Separating
Divided
Divided
Mitosis Video