Download Mitosis

Biology is the only subject in
which multiplication is the same
thing as division…
Regents Biology
2006-2007
MITOSIS:
Making New Cells
Making New DNA
Regents Biology
Where it all began…
You started as a cell smaller than
a period at the end of a sentence…
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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
4 chromosomes
in
thisBiology
organism
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DNA in chromosomes in cell
getting ready to divide
Chromosomes of Human Female
46 chromosomes
23 pairs
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Chromosomes of Human Male
46 chromosomes
23 pairs
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Paired bases
 DNA structure

double helix
 2 sides like a ladder
 Bases match together

A pairs with T
A:T

C pairs with G
C:G
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phosphate
sugar
N base
Watson and Crick
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Copying DNA
 Matching bases allows
DNA to be easily copied
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Making new DNA
 Copying DNA
replication
 DNA starts as a double-stranded
molecule

 matching bases (A:T, C:G)

then it unzips…
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DNA replication
 Strands “unzip” at the weak bonds
between bases
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DNA replication
DNA bases
in nucleus
 Enzyme
DNA polymerase
 adds new bases

DNA
polymerase
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Copying DNA
 Build daughter DNA
strand
use original parent
strand as “template”
 add new matching
bases
 synthesis enzyme =
DNA polymerase

DNA
Polymerase
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New copies of DNA
 Get 2 exact copies of DNA to split
between new cells
DNA
polymerase
DNA
polymerase
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Copied & Paired Up Chromosomes
centromere
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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
4Regents
double-stranded
cell
nucleus
Mitosis: Dividing DNA & cells
 Stage 1: cell copies DNA
Copy DNA!
DNA
cell
nucleus
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(interphase)
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