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Copy of mitosis 2010
1. Mitosis
Biology is the only
subject in which
multiplication is the
same thing as division…
2. Where it all began…
You started as a cell smaller than
a period at the end of a sentence…
3. And now look at you!
How did you
get from
there to
here?
4. Mitosis!
The fertilized egg must divide…
and divide….
and divide….
and divide…
5. Why do cells divide…
for reproduction
one celled organisms (clones)
asexual reproduction amoeba
for growth & development
from fertilized egg to multi-celled organism
for repair
starfish
replace cells that die from
normal wear & tear or from injury
6. Dividing cells…
What has to be copied
DNA
organelles
cell membrane
lots of other
molecules
• enzymes
plant cell animal cell
7. Copying DNA
A dividing cell duplicates its DNA
creates 2 copies of all DNA
sends the 2 copies to opposite ends of the
cell
splits into 2 daughter cells
the DNA starts
DNA
loosely wound in
cell the nucleus
If you tried to divide
it like that, it could
nucleus tangle & break
8. Organizing & packaging DNA into
chromosomes…
DNA
cell
nucleus DNA has been
“wound up”
DNA in chromosomes in
everyday “working” cell cell
nucleus
4 chromosomes DNA in chromosomes in cell
in this organism getting ready to divide
12. Copying & packaging DNA
When cell is ready to divide…
copy DNA first, then…
coil up doubled chromosomes
like thread on a spool…
• now can move DNA around cell without having it
tangle & break
Coil DNA into
Copying DNA compact chromosomes
13. Copying DNA…
chromosomes in cell
DNA in chromosomes
cell 4 single-stranded chromosomes
duplicated chromosomes
nucleus
duplicated
chromosomes cell
4 double-stranded chromosomes
nucleus
18. Mitosis Vocabulary
Centrioles – small, cylinder shaped structures found near
the nucleus, involved in mitosis
Only in animal cells
Aster – star like structure made of microtubules that
extend from centrioles
Spindle – web like structure made up of microtubule
fibers. It arranges and moves the chromosomes around.
19. Interphase DNA found as chromatin
Cell grows & produces
more molecules &
organelles
DNA and centrioles
replicate
DNA Three mini stages:
G1
cell
S
G2
nucleus
Interesting things
happen!
21. Prophase
Chromosomes become
visible
DNA is wound into
chromosomes
Nuclear membrane and
duplicated
nucleolus breakdown
chromosomes Centrioles move to
opposite poles
Spindle and asters
cell begins to form
Chromosomes
nucleus pair up!
22. Metaphase
Spindle is fully developed
Sister chromatids line up
at the equator
Chromatids are attached
to the spindle at the
centromere
Chromosomes
meet in the
middle!
23. Anaphase Sister chromatids
separate
One complete set of
chromosomes goes to
each pole
Spindle pull chromatids
to opposite poles
Cytokinesis begins
Chromosomes get
pulled apart!
24. Telophase Chromosomes reach
opposite poles
Nuclear membrane and
nucleolus reappear
Spindle disappears
Chromosomes unravel
Cytokinesis is completed
Now there are
two!
31. How does mitosis differ in plants?
Plant cells do not have centrioles
Plant cells do not pinch in half
Cytokinesis is accomplished through the
formation of a cell plate between the two
daughter cells
34. Cell Turnover – the speed of
mitosis
The time it takes for a cell to
complete one cycle can vary
between a couple of minutes to
days.
Cells that are continuously being
worn away have a rapid turnover.
E.g. skin, epithelial cells, RBC, etc.
Cells which make up organs such as
the eye and the brain do not multiply
very often if ever once they reach
adult size.
35. Control of the Cell Cycle
Growth & division are carefully regulated
The protein cyclin regulates the cell cycle.
Cyclin is produced during interphase.
Once the cyclin reaches a certain level it
triggers mitosis.
During mitosis most of the cyclin
is destroyed.
The new daughter cells must
produce new cyclin before a
second mitosis can occur
36. How do we know?
Scientists found that when cyclin is
injected into a nondividing cell, that cell
forms a spindle
They then found the amount of cyclin
increased and decreased in timing with
the cell cycle
37. Other Regulatory Proteins
Internal
Proteins in the cell respond to events inside
the cell
• E.g. makes sure cell does not enter mitosis until all
chromosomes have been replicated
• E.g. No anaphase until all chromosomes are
attached to the spindle
38. Other Regulatory Proteins
External
Proteins that respond to events outside the
cell
• May stimulate growth – e.g. wound healing,
embryonic development
• May slow growth – e.g. prevent excessive growth,
keep tissues from disrupting each other
39. Cancer – cell division gone wild!
Cancer – uncontrolled
mitosis
Don’t respond to normal
cellular controls
Cells divide excessively
Many causes resulting in
gene mutations (often in
gene p53)
• Smoking, radiation, viral
infection, heredity
40. Cancer – cell division gone wild!
Tumor – a mass of abnormal cells
Benign tumor – abnormal cells remain in
original location
Malignant tumor – abnormal cells leave the
original site and impair the function of one or
more organs
41. Biology is the only subject in
which multiplication is the same
thing as division…
2006-2007
Notes de l'éditeur
Unicellular organisms Cell division = reproduction Reproduces entire organism& increase population Multicellular organisms Cell division provides for growth & development in a multicellular organism that begins as a fertilized egg Also use cell division to repair & renew cells that die from normal wear & tear or accidents
DNA – deoxyribonucleic acid, the hereditary material of the cell. Chromatin – thin twisted strands of DNA wrapped around proteins How DNA is found in a nondividing cell Histones – proteins DNA is wrapped around in chromatin Chromosomes/chromatid – short, thick, condensed DNA/protein structures found in dividing cells Sister chromatids – double chromosome found during cell division Centromere – region that connects sister chromatids and where the spindle attaches to the chromatids
A mnemonic to help remember the stages of mitosis.