Transcript cell division

CELL DIVISION
© 2006 Mesoblast Limited www.mesoblast.com
© 2007 Paul Billiet ODWS
Think
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Of how many cells are you composed?
When an organism grows bigger, do you get more
cells or just bigger cells or both?
When do your cells divide the fastest? Slowest?
Do cells ever stop dividing?
Are all cells capable of division and replacement?
http://www.nobel.se/medicine/laureates/2001/press.html
Cell division is a fundamental process
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All cells come from pre-existing cells
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It is necessary to replace worn out /damaged cells
in multicellular organisms
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It is required for growth in multicellular organisms
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It is necessary for reproduction in unicellular or
multicellular organisms
© 2007 Paul Billiet ODWS
Cell division replaces worn out/
damaged cells
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All cells die after a certain number of divisions –
apoptosis.
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At any time some cells are dividing and some cells
are dying.
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Childhood – Cell division > cell death
Adulthood – Cell division = cell death
Aging – Cell division < cell death
http://www.nobel.se/medicine/laureates/2001/press.html
Cell division is required for growth
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Organisms don’t get bigger by increasing cells size.
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An increase in size will require an increase in surface area
to volume ratio.
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Cell division subdivides the cytoplasm into small units
(cells) surrounded by plasma membranes
© 2007 Paul Billiet ODWS
Cell division is required for growth
Cell division is necessary for
reproduction
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It is necessary for
reproduction in
unicellular or
multicellular
organisms.
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Binary fission
Mitosis
Meiosis
© 2007 Paul Billiet ODWS
Reproduction in Prokaryotes
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Prokaryotes have
no nucleus
They have a single
circular chromosome
Prokaryotes simply
divide their cells in
two by binary
fission
http://instruct1.cit.cornell.edu/
© 2007 Paul Billiet ODWS
Reproduction in Eukaryotes
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Eukaryotes must divide their nucleus (and
other organelles such as mitochondria) in
preparation for cell division (mitosis or
meiosis)
Before the nucleus divides the genetic
material replicates (duplicates)
© 2007 Paul Billiet ODWS
Mitosis
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Mitotic division
results in genetically
identical eukaryotic
cells (a clone)
Mitosis is the basis of
asexual reproduction
Results in a cell with 2
of each chromosome –
diploid.
© 2007 Paul Billiet ODWS
© Tyler Junior College, (no
commercial use allowed - contact
[email protected] for permission to use)
Mitosis
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The process of cell division that results in the
production of two daughter cells from a single
parent cell.
The daughter cells are identical to one
another and to the original parent cell.
Mitosis is a stage of the cell cycle
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Interphase
Mitosis
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Prophase
Metaphase
Anaphsase
Telophase
Cytokinesis
Interphase – Cell prepares for
division
Animal Cell
 Cell growth
 Organelles duplicated
 More enzymes produced
 DNA replicates
 Centrioles duplicated
Plant Cell
 Cell growth
 Organelles duplicated
 More enzymes produced
 DNA replicates
Stages of Interphase
Interphase – Cell prepares for
division
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Prophase – Cell prepares for
nuclear division
Animal Cell
 DNA packaged into
chromosomes
(chromosomes condense)
 Centrioles move to
opposite ends of cell
 Spindle fibers form
 Nuclear envelope breaks
down
Plant Cell
 DNA packaged into
chromosomes
(chromosomes condense)
 Spindle fibers form
 Nuclear envelope breaks
down
Prophase – Cell prepares for
nuclear division
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Metaphase – chromosomes
prepared for division
Animal Cell
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Chromosomes line up at
center of cell.
Spindle fibers attach to
daughter cells at
centromere.
Plant Cell
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Chromosomes line up at
center of cell.
Spindle fibers attach to
daughter cells at
centromere.
Metaphase – chromosomes
prepared for division
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Anaphase – chromosomes divide
Animal Cell
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Spindle fibers pull
chromosomes apart.
½ of each chromosome
(called a chromatid) moves
to each daughter cell.
Plant Cell
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Spindle fibers pull
chromosomes apart.
½ of each chromosome
(called a chromatid) moves
to each daughter cell.
Anaphase – chromosomes divide
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Telephase – Cytoplasm starts to
divide
Animal Cell
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DNA spreads out
Nuclear envelope forms
around each set of
chromosomes
Cell membrane invaginates
Plant Cell
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DNA spreads out
Nuclear envelope forms
around each set of
chromosomes
Cell wall forms between
the 2 nuclei to form 2
daughter cells
Telephase – Cytoplasm starts to
divide
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Cytokinesis – Two new cells
Animal Cell
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Cytoplasm continues to
squeeze together and
pinches into 2 new cells.
Each daughter cell gets half
of the organelles.
Plant Cell
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Cell plate begins to form
new cell membranes
between the 2 daughter
cells.
New cell walls form
around the cell membranes.
Meiosis
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Meiosis results in a halving of the
chromosome number in preparation for
fertilisation
Meiosis shuffles genes in new combinations
Meiosis results in genetically different cells
Meiosis and fertilisation are the basis of
sexual reproduction
© 2007 Paul Billiet ODWS
Different kinds of cells divide at
different rates
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E. coli – 20 minutes
Yeast – 2 hours
Amoeba – a few days
Human embryo cell – 15-20 minutes
Human adult cell – 8 hours or more
Frog egg cell – 30 minutes
http://www.nobel.se/medicine/laureates/2001/press.html
Cell cycle video
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Bill Nye
Cell Cycle Rap
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Cell Cycle Rap