Transcript mitosis. - Cloudfront.net

Mitosis Notes
Cell Division
All cells are derived from pre-existing
cells
 New cells are produced for growth
and to replace damaged or old cells
 Differs in prokaryotes (bacteria) and
eukaryotes (protists, fungi, plants, &
animals)

2
Keeping Cells Identical
The instructions for
making cell parts
are encoded in the
DNA, so each new
cell must get a
complete set of the
DNA molecules
3
DNA Replication
DNA must be
copied or
replicated before
cell division
 Each new cell will
then have an
identical copy of
the DNA

Original DNA
strand
Two new,
identical DNA
strands
4
Mitosis Notes
 Cells
divide to make more
cells…this is called mitosis.
 All organisms start as just one
cell and continue to divide and
make more. Humans have over
50,000,000,000,000 cells.
Mitosis
Mitosis is the division of the nucleus in
eukaryotic cells. Mitosis has 6 steps.
 In mitosis the DNA is copied so that each
cell gets a copy.
 The DNA is condensed into a
chromosome. Humans have 46
chromosomes.

Chromosomes Notes


Each of the cells in your body have the
same 46 chromosomes. You get 23
chromosomes from each parent.
Not all species have the same number of
chromosomes. Corn has 20, flies have 10,
chimpanzees have 48.
Chromosome Notes

Each chromosomes has a central region
called a centromere that is an important
attachment point for mitosis.
Chromosome Notes

The cell providing the
DNA to be copied is
the “parent cell,” the
cells that are created
are identical “daughter
cell.”
Chromosome

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A chromosome contains
the DNA for the
organism.
During mitosis the
chromosome divides into
two chromatids that are
copied during mitosis.
These chromatids are
“sister chromatids”
Karyotype



First 22 pairs are called
autosomes
Last pair are the sex
chromosomes
XX female or XY male
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Boy or Girl?
The Y Chromosome Decides
Y - Chromosome
X - Chromosome
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Prokaryotic Chromosome

The DNA of
prokaryotes
(bacteria) is one,
circular
chromosome
attached to the
inside of the cell
membrane
13
Cell Division in
Prokaryotes
Parent cell



Prokaryotes such as
bacteria divide into 2
identical cells by the
process of binary
fission
Single chromosome
makes a copy of itself
Cell wall forms between
the chromosomes
dividing the cell
Chromosome
doubles
Cell splits
2 identical daughter cells
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Types of Cell Reproduction


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
Asexual reproduction involves a single cell
dividing to make 2 new, identical daughter
cells
Mitosis & binary fission are examples of
asexual reproduction
Sexual reproduction involves two cells (egg &
sperm) joining to make a new cell (zygote)
that is NOT identical to the original cells
Meiosis is an example
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The cell cycle

Some cells divide constantly like skin cells
and stomach cells. Some cells divide only
every 10 years. Actively dividing cells go
through the cell cycle. The cell cycle has
four parts.
The Cell Cycle



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G1- (GAP) Each chromosome has 1
chromatid. Cells spend most of their time
here if they are not dividing.
S- (Synthesis) this is when DNA is copied.
The chromosome goes from one chromatid
to 2 chromatids.
G2- Is the period between S and mitosis.
The cell prepares for Mitosis
M- is Mitosis
DNA Copied
Cells prepare for Division
Cells
Mature
Daughter
Cells
Cell Divides into Identical cells
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Interphase

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During Interphase chromosomes are
copied (sister chromosome) but remain in
loose structures called chromatin.
All the organelles are copied.
Interphase is not technically part of mitosis
because mitosis is division of the nucleus
and Interphase involves division of other
organelles.
Prophase

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Prophase means “the before stage.”
Prophase is the start of mitosis.
Chromatin condenses into chromosomes.
The microtubules condense into
centrisomes which move to opposite poles
of the cell.
The nuclear membrane starts to dissolve.
Spindle fibers begin to form to help line the
chromosomes up.
Metaphase

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Chromosomes line up on the equator of the
cell. Spindle fibers attach to the
centromeres of the chromatids.
Everything is now aligned for the rest of
division to occur.
Anaphase

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Chromatids (or pairs of chromosomes)
separate and move to opposite ends of the
cell.
The spindle fibers contract and the
chromosomes are pulled towards the
centrioles.
Telophase

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In telophase the cell divides. Two new
nuclei begin to form.
The chromosomes are at the poles and the
spindle fibers disintegrate.
Chromosomes begin to appear as
chromatin (the threads not the rods).
This is the end of mitosis.
Cytokinesis


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The organelles get divided evenly into each
(daughter cell). Each cell has identical
chromosomes in their own nucleus.
Plant and animal cells divide differently. Plants
form a new cell wall that cuts the two cells apart.
Animal cells form actin fibers around the
equator of the cell and this pinches the cell in
half.
Cytokinesis isn’t part of mitosis (doesn’t involve
the nucleus). After Cytokinesis we go back to
G1 and start over.
White Board
Mitosis Review
What part of mitosis is shown?
What part of mitosis is shown?
What part of mitosis is shown?
What part of mitosis is shown?
What part of mitosis is shown?
In what part of mitosis do
chromosomes double?
In what part of mitosis do
chromosomes attach to spindle
fibers?
In what part of mitosis does the
nuclear membrane start to re-form?
In what part of mitosis do the
chromosomes line up at the cell
equator?
When do the copied chromosomes
move to opposite ends of the cell?