Download Dave Cooke Mitosis

Biology is the only subject in
which multiplication is the same
thing as division…
AP Biology
2006-2007
The Cell Cycle:
Cell Growth, Cell Division
AP Biology
2006-2007
Where it all began…
You started as a cell smaller than
a period at the end of a sentence…
AP Biology
And now look at you…
AP Biology
How did you
get from there
to here?
Getting from there to here…
 Cell division
reproduction of cells
 continuity of life

 reproduction
 unicellular organisms
 growth
 repair & renew
 Cell cycle

AP Biology
life of a cell from
origin to division into
2 new daughter cells
amoeba
Getting the right stuff
 What is passed on to daughter cells?

exact copy of genetic material = DNA
 mitosis

division of organelles & cytoplasm
 cytokinesis
chromosomes (stained orange)
in kangaroo rat epithelial cell
AP Biology
notice cytoskeleton fibers
Copying DNA
 Dividing cell duplicates DNA
separates each copy to
opposite ends of cell
 splits into 2 daughter cells

 human cell duplicates ~3 meters DNA
 each daughter cell gets complete
identical copy
 error rate = ~1 per 100 million bases
 3 billion base pairs
mammalian genome
 ~30 errors per cell cycle
 mutations

AP Biology
A bit about DNA
DNA
 DNA is organized in
chromosomes
histones
double helix DNA molecule
 associated proteins =
histone proteins
 DNA-protein complex =
chromatin
chromatin

 organized into long
thin fiber
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duplicated chromosome
human
chromosomes
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Chromosome structure
scaffold
protein
chromatin loop
DNA nucleosome
histone
rosettes of
chromatin loops
chromosome
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DNA double helix
Copying DNA with care…
 After DNA duplication, chromatin condenses


coiling & folding to make a smaller package
from DNA molecule to chromatin to highly
condensed mitotic chromosome
mitotic chromosome
DNA
chromatin
AP Biology
Mitotic Chromosome
 Duplicated chromosome
2 sister chromatids
 narrow at centromeres
 contain identical
copies of original DNA

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M
Mitosis
Cell cycle
 Cell has a “life cycle”
cell is formed from
a mitotic division
cell grows & matures
to divide again
G1, S, G2, M
epithelial cells,
blood cells,
stem cells
AP Biology
G2
Gap 2
S
Synthesis
cell grows & matures
to never divide again
liver cells
G1G0
brain / nerve cells
muscle cells
G1
Gap 1
G0
Resting
M
Mitosis
Cell Division cycle
 Phases of a dividing
G2
Gap 2
cell’s life

interphase





S
Synthesis
G0
Resting
cell grows
replicates chromosomes
produces new organelles, enzymes, membranes…
G1, S, G2
mitotic phase
 cell separates & divides chromosomes
 mitosis
 cell divides cytoplasm & organelles
 cytokinesis
AP Biology
G1
Gap 1
Interphase
 90% of cell life cycle

cell doing its “everyday job”
 produce RNA, synthesize proteins/enzymes

prepares for duplication if triggered
 Characteristics


AP Biology
nucleus well-defined
DNA loosely
packed in long
chromatin fibers
Interphase
 Divided into 3 phases:

G1 = 1st Gap
 cell doing its “everyday job”
 cell grows

S = DNA Synthesis
 copies chromosomes

G2 = 2nd Gap
 prepares for division
 cell grows
 produces organelles,
proteins, membranes
AP Biology
Interphase
 Nucleus well-defined
chromosome duplication
complete
 DNA loosely packed in
long chromatin fibers

 Prepares for mitosis

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produces proteins &
organelles
Mitosis
 Dividing cell’s DNA between
2 daughter nuclei

“dance of the chromosomes”
 4 phases
prophase
 metaphase
 anaphase
 telophase

AP Biology
Prophase
 Chromatin condenses

visible chromosomes
 chromatids
 Centrioles move to opposite

poles of cell
Protein fibers cross cell to form
mitotic spindle



microtubules
coordinates movement of
chromosomes
actin, myosin
 Nucleolus disappears
 Nuclear membrane breaks down
AP Biology
Transition to Metaphase
 Prometaphase

spindle fibers attach to
centromeres
 creating kinetochores

microtubules attach at
kinetochores
 connect centromeres to
centrioles

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chromosomes begin
moving
Metaphase
 Chromosomes align
along middle of cell

metaphase plate
 meta = middle
spindle fibers coordinate
movement
 helps to ensure
chromosomes separate
properly

 so each new nucleus
receives only 1 copy of
each chromosome
AP Biology
AP Biology
Anaphase
 Sister chromatids separate
at kinetochores
move to opposite poles
 pulled at centromeres
 pulled by motor proteins
“walking”along
microtubules

 actin, mysoin
 increased production of
ATP by mitochondria
 Poles move farther apart
polar microtubules
AP Biology lengthen

Separation of chromatids
 In anaphase, proteins holding together sister
chromatids are inactivated

separate to become individual chromosomes
1 chromosome
AP
Biology
2 chromatids
2 chromosomes
Chromosome movement
 Kinetochores use
motor proteins that
“walk” chromosome
along attached
microtubule

AP Biology
microtubule
shortens by
dismantling at
kinetochore
(chromosome) end
Telophase
 Chromosomes arrive at
opposite poles
daughter nuclei form
 nucleoli form
 chromosomes disperse

 no longer visible under
light microscope
 Spindle fibers disperse
 Cytokinesis begins

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cell division
Cytokinesis
 Animals

constriction belt of
actin microfilaments
around equator of cell
 cleavage furrow forms
 splits cell in two
 like tightening a draw
string
AP Biology
Cytokinesis in Animals
(play Cells Alive movies here)
AP Biology
(play
Thinkwell movies here)
Mitosis in whitefish blastula
AP Biology
Mitosis in animal cells
AP Biology
Cytokinesis in Plants
 Plants

cell plate forms
 vesicles line up at
equator
 derived from Golgi
 vesicles fuse to form
2 cell membranes

new cell wall laid
down between
membranes
 new cell wall fuses
AP Biology
with existing cell wall
Cytokinesis in plant cell
AP Biology
Mitosis in plant cell
AP Biology
onion root tip
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Evolution of mitosis
 Mitosis in
chromosome:
double-stranded replication
of DNA
DNA
eukaryotes
likely evolved from
binary fission in
bacteria
single circular
chromosome
 no membranebound organelles

AP Biology
Origin of
replication
elongation of cell
ring of
proteins
cell pinches
in two
Evolution of
mitosis
 A possible
progression of
mechanisms
intermediate
between binary
fission & mitosis
seen in modern
organisms
prokaryotes
(bacteria)
protists
dinoflagellates
protists
diatoms
eukaryotes
yeast
eukaryotes
animals
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Dinoflagellates
 algae
“red tide”
 bioluminescence

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Diatoms
 microscopic algae
marine
 freshwater

AP Biology
Any Questions??
AP Biology
2006-2007