Download and divide…

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MITOSIS:
Making New Cells
Making New DNA
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Where it all began…
You started as a cell smaller than
a period at the end of a sentence…
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And now look at you…
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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


for reproduction
asexual reproduction (clones)
amoeba
 Multi-celled organisms

for growth & development
 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
creates 2 copies of all DNA
 separates the 2 copies to opposite ends
of the cell
 splits into 2 daughter cells

DNA
cell
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nucleus
 But the DNA starts
loosely wound in
the nucleus
 If you tried to divide
it like that, it could
tangle & break
Organizing & packaging DNA
DNA
cell
nucleus
DNA has been
“wound up”
DNA in chromosomes in
everyday “working” cell
cell
nucleus
chromosomes
in
thisBiology
organism
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DNA in chromosomes in cell
getting ready to divide
 Chromosome – condensed DNA bound in the
center by a centromere
centromere
chromatin
chromatid
Chromatin - condensed single strand DNA
Chromatid
– each strand of doubled chromosome
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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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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
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Copying DNA
Coil DNA into
compact chromosomes
double-stranded
human chromosomes
ready for mitosis
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DNA must be duplicated…
chromosomes in cell
DNA in chromosomes
cell
nucleus
4 single-stranded chromosomes
duplicated chromosomes
duplicated
chromosomes
Biology chromosomes
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double-stranded
cell
nucleus
Mitosis: Dividing DNA & cells
 Stage 1: cell copies DNA
DNA
cell
nucleus
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• Cell growth
• DNA replicates
• Centrioles replicate
and go to opposite
sides of the cell
• Divided into 3 parts
• G1, S, G2
(interphase)
Time Span
 Cyclin
A protein that determines the cell cycle
 Cyclin increases until it reaches a certain
point then cell starts mitosis

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Mitosis: Dividing DNA & cells
 Stage 2: DNA winds into chromosomes

DNA is wound up into chromosomes to
keep it organized
duplicated chromosomes
Wind up!
cell
nucleus
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(prophase)
Mitosis: Dividing DNA & cells
 Stage 3: Chromosomes line up
chromosomes line up in middle
 attached to protein “cables” that will
help them move

Line up!
duplicated chromosomes
lined up in middle of cell
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(metaphase)
Mitosis: Dividing DNA & cells
 Stage 4: Chromosomes separate
chromosomes split, separating pairs
 start moving to opposite ends

Separate!
chromosomes split &
move to opposite ends
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(anaphase)
Mitosis: Dividing DNA & cells
 Stage 5: Cell starts to divide
cells start to divide
 nucleus forms again

Divide!
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(telophase)
Mitosis: Dividing DNA & cells
 Stage 6: DNA unwinds again
cells separate
 now they can do their every day jobs

Bye Bye!
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(cytokinesis)
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
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metaphase
anaphase
telophase
Any Questions??
Any Questions??
Regents Biology
2009-2010
Asexual Reproduction
1. Binary Fission


organism divides into
2 equal parts
Ex: bacteria,
protozoan
2. Budding


Parent divides into 2
unequal parts
Ex: yeast, Hydra
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3. Spores


Thickly coated
cells
Ex: Mold
4. Regeneration


Ability to regrow
lost body parts
Ex: Planaria
5. Vegetative
Propagation
Using roots, stems,
and leaves to make
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a new plant

Mitosis & Cancer:
When Making New Cells
Goes Terribly Wrong!
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When is mitosis a good thing?
 When you have to add or replace cells
growth & development
 repair
 replacement

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When is mitosis a BAD thing
 When cells reproduce & they are not
needed
these cells take over organs, but don’t
do the right job
 they just keep making copies
 cancer

 damages organs
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Why would cells just make copies?
 If DNA gets damaged, cells stop listening
to correct instructions

Mutations - carcinogens
 Causes of mutations:




UV radiation
chemical exposure
radiation exposure
heat
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



cigarette smoke
pollution
age
genetics
Tumors
 Benign tumor
abnormal cells remain at original site as
a lump
 most do not cause serious problems &
can be removed by surgery

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Tumors
 Malignant tumor

cells leave original site
 carried by blood system to other tissues
 start more tumors

damage functions of organs throughout body
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Treatments for cancers
side effects
 Treatments kill rapidly dividing cells

chemotherapy
 poisonous drugs that kill rapidly dividing cells

radiation
 high energy beam kills rapidly dividing cells
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Any Questions??
Any Questions??
Regents Biology
2009-2010