Transcript Mitosis

Chapter 8 Notes
8.1 – 8.11 Cell Reproduction and
Growth
Where are we in our
tour of the cell?
WHY DO CELLS DIVIDE??
to make more cells for replacing old,
worn out or damaged cells
 for growth and development of an
organism
 create a new organism; reproduction
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(single-celled)
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BINARY FISSION
– division of a single celled
organism that creates a whole new organism (Bacteria)
The Cell Cycle
The cell cycle is the a series
of events cells go through to
divide and create more cells.
Some cells divide constantly:
cells in the embryo, skin cells,
gut lining cells, etc.
Other cells divide rarely or
never: only to replace
themselves (liver, muscle
cells, nerve cells)
Interphase
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Most of the cycle was called
interphase.
During interphase, the cell
increases in size, but the
chromosomes are invisible.
The 3 stages of interphase are
called G1, S, and G2.
CdK and Cyclin are 2 protein
enzymes involved in regulating
the cell cycle.
G1 and G2
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Both stages are part of
interphase, and include the cell
increases in size
(G=GROWTH!)
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G1 comes before S phase, and
G2 comes after S phase
S phase
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S phase = “Synthesis”
S phase involves DNA
synthesis; creating a copy of
the DNA from one cell to
send a copy into the new
cell.
The process of copying of DNA
(DNA Replication) will be
covered in more detail in Ch. 10!
Duplicated chromosomes
AFTER S
BEFORE S
S phase –
DNA and
Chromosomes
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DNA contains all the genetic
information for creating and running
the organism.
Chromosome- a single long strand of
DNA wrapped around protein, clumped into
an X shaped
Sister chromatids – Half of the ALREADY
DUPLICATE X SHAPE of a chromosome
(IDENTICAL!)
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Each chromosome has a central constricted
region called a centromere that serves as
an attachment point for each sister
chromatid.
M phase
M phase = “Mitosis”
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Mitosis – division of the
chromosomes and organelles that
were duplicated in S phase
M phase sends a copy of all the
genetic information and
necessary organelles into the
new cell.
Occurs in most somatic cells (All
cells of the body EXCEPT the
reproductive cells!)
Machinery of Mitosis
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Spindle fibers - The chromosomes are
pulled apart by these extending strands of
microtubules.
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The spindle fibers are attached to each
centromere.
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Centrioles (in animal cells) and
anchored on the other end of the spindle
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When the spindle fibers contract, the
chromosomes are pulled to the opposing
poles.
4 stages of mitosis
1)
2)
3)
4)
Prophase
Metaphase
Anaphase
Telophase
(PMAT)
Prophase
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First stage of mitosis.
1) The chromosomes condense.
2) The nuclear envelope disappears.
3) The centrioles move to opposite
poles.
*During interphase, the pair of centrioles
were together just outside the nucleus.
4) The spindle starts to form, growing
out of the centrioles towards the
chromosomes.
Metaphase
1) Short resting period
where the chromosomes
are lined up on the
equator of the cell
(MIDDLE) with the
centrioles at opposite
ends.
2) The spindle fibers
attached to the
centromeres.
Anaphase
1)
The centromeres
separate.
2) The spindle fibers
contract, and the
chromosomes are pulled to
opposite poles, towards
the centrioles.
Telophase
1) The cell cytoplasm begins
to divide. (cleavage furrow)
2) The chromosomes are at
the poles of the spindle.
3) The spindle disintegrates
4) The nuclear envelope
forms around the two
separated sets of
chromosomes.
Cytokinesis
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Cytokinesis- separation of the
cytoplasm into 2 separate cells.
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Last stage of cell division (NOT
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Cell plate:
In plant cells, a
new cell wall
made of
cellulose forms
between the 2
new nuclei
considered part of mitosis)
The organelles get divided up
into the 2 daughter cells,
whichever cell they find
themselves in.
Cleavage
furrow:
In animals, a
indentation
begins from the
outside, pinching
inwards.
Summary of Mitosis
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Prophase:
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Metaphase
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Chromosomes lined up on equator of spindle
centrosomes at opposite ends of cell
Spindles attach to centromeres on the chromosomes
Anaphase
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Chromosomes condense
Nuclear envelope disappears
centrosomes move to opposite sides of the cell
Spindle forms
Centromeres divide: each 2-chromatid chromosome
becomes two 1-chromatid chromosomes
Chromosomes pulled to opposite poles by the spindle
Telophase
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Chromosomes de-condense
Nuclear envelope reappears
Cytokinesis: the cytoplasm is divided into 2 cells
Animations
Mitosis and
Cytokinesis
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Binary Fission
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Cancer
Cancer
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Cancer is a disease of uncontrolled cell division.
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It starts with a single cell that loses its control mechanisms due to a
genetic mutation. (loss of CdK/cyclin functioning).
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Cancer cells enter the S phase without waiting for a signal.
Normal cells are mortal. This means that they can divide about 50
times and then they lose the ability to divide, and eventually die.
Cancer cells will continue to divide
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Tumor - a small mass of cells.
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Benign – stops growing and stays at original site.
Malignant – continues to grow in a new site from origninal.
Cancer Progression
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Metastasis- cancer cells will break loose and
move through the blood supply to other parts of
the body, where they start to multiply.
There are many different forms of cancer, affecting
different cell types and working in different ways.
All cancers start mutations in specific genes. The
mutations are caused by radiation (i.e. UV),
certain chemicals (carcinogens- nicotine,
pesticides, plastics), and various random events
during DNA replication.
Cancer Treatment
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Two basic treatments:
1)
2)
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Surgery to remove the tumor
Radiation and/or chemicals to kill actively dividing cells.
Radiation and chemotherapy are aimed at killing
actively dividing cells, but killing all dividing cells is
lethal.
If any tumor cells are resistant to the chemical
treatment, they will survive and multiply. The cancer
seems to have disappeared, but it comes back a few years
later in a form that is resistant to chemotherapy. Using
multiple drugs can decrease the risk of relapse: it’s hard for
a cell to develop resistance to several drugs at the same
time.
Mitosis Skit
Now you will show mitosis!
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NEED (per group)
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4
2
4
2
1
spindles (white strings)
nuclear envelopes (long strings)
chromatids (2 chromosomes) = 4 people
centrioles (2 people)
narrator (no reading from book!)