Download Biology is the only subject in which multiplication is the same

Cellular Mitosis
Notes
Biology is the only subject
in which multiplication is
the same thing as division…
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2006-2007
MITOSIS:
Making New Cells
Making New DNA
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Where it all began…
We all start as a cell smaller than
a period at the end of a sentence…
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And now look what can
happen…
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How did you
get from there
to here?
Getting from there to here…
• Going from egg to baby….
the original fertilized egg has to divide…
and divide…
and divide…
and divide…
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Why do cells divide…
 One-celled organisms
1.
2.
for reproduction
asexual reproduction (clones)
amoeba
 Multi-celled organisms
1.
for growth & development

2.
from fertilized egg to adult
for repair & replacement

replace cells that die from
normal wear & tear or from injury
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starfish
Dividing cells…
• What has to be copied
–
–
–
–
DNA
organelles
cell membrane
lots of other
molecules
• enzymes
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plant cell
animal cell
Copying DNA
•
A dividing cell duplicates its DNA
1. creates 2 copies of all DNA
2. separates the 2 copies to opposite ends of the
cell
3. splits into 2 daughter cells
DNA
cell
nucleus
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 But the DNA starts
loosely wound in
the nucleus
 If you tried to divide
it like that, it could
tangle & break
Copying & packaging DNA
•
When cell is ready to divide…
1. copy DNA first, then…
2. chromosomes COIL UP
like thread on a spool…
•
now can move DNA around cell without having it
tangle & break
Copying DNA
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Coil DNA into
compact chromosomes
Organizing & packaging DNA
DNA
cell
DNA has been
“wound up”
nucleus
DNA in chromosomes in
everyday “working” cell
cell
nucleus
4 chromosomes
in this organism
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getting ready to divide
DNA must be duplicated…
chromosomes in cell
DNA in chromosomes
cell
4 single-stranded chromosomes
duplicated chromosomes
nucleus
duplicated
chromosomes
4 double-stranded chromosomes
cell
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nucleus
double-stranded
human chromosomes
ready for mitosis
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Chromosomes of Human Female
46 chromosomes
23 pairs
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Chromosomes of Human Male
46 chromosomes
23 pairs
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Mitosis: Dividing DNA & cells
• Stage 1: cell
copies DNA
DNA
cell
nucleus
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interphase
Mitosis: Dividing DNA & cells
• Stage 2: DNA
winds up into chromosomes
– DNA is wound up into chromosomes to keep it
organized
duplicated chromosomes
(prophase)
cell
nucleus
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Mitosis: Dividing DNA & cells
• Stage 3: Chromosomes line up
– chromosomes line up in middle
– attached to protein “cables” that will help them
move
metaphase
duplicated chromosomes
lined up in middle of cell
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Mitosis: Dividing DNA & cells
• Stage 4: Chromosomes separate
– chromosomes split, separating pairs
– start moving to opposite ends
anaphase
chromosomes split &
move to opposite ends
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Mitosis: Dividing DNA & cells
• Stage 5: Cell starts to divide
– cells start to divide
– nucleus forms again
telophase
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Mitosis: Dividing DNA & cells
• Stage 6: DNA unwinds again
– cells separate
– now they can do their every day jobs
cytokinesis
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New “daughter” cells
• Get 2 exact copies of original cells
– same DNA
– “clones”
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Cell division in Animals
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Mitosis in whitefish embryo
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Mitosis in plant cell
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onion root tip
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Overview of mitosis
interphase
I.P.M.A.T.C.
prophase
Please Make Another Two Cells
cytokinesis
metaphase
anaphase
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telophase
Any Questions??
Any Questions??
2009-2010