Download Mitosis Cancer 14 - Mercer Island School District

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Mitosis
Mitosis is the type of cell division that
occurs for growth (adding new cells)
and repair (replacing old or damaged
cells).
It results in two daughter cells that
have identical chromosomes to the
parent cell.
Almost every cell in the human
body has an identical set of 46
chromosomes, produced
through the process of mitosis.
Structure of eukaryotic chromosomes
During most of a cell’s life cycle, the DNA strands are
so long and thin that they are not visible under a
microscope. The loose DNA is called chromatin.
Prior to cell division, the DNA coils several times
around proteins (histones) to form shorter, thicker
structures called chromosomes that are visible under a
microscope.
Coiling of DNA
http://www.youtube.com/watch?v=N5zFOScowqo
Cell Cycle Animation
During G1:
Normal cell activities.
During S:
Synthesis of new DNA
Each chromosome is
replicated,
forming 2 identical copies of
each.
Interphase
(between cell divisions):
G1, S and G2.
Chromosomes are not visible.
During G2:
Final preparations for cell
division.
G1: cells grow, carry out their
normal functions and replicate
their organelles
Synthesis: cells make a copy
of nuclear DNA (at the end of
this phase there are 2 sets of
DNA).
G2: cells continue to carry out
normal functions and
additional growth occurs
Chromosome/Centromere/Sister Chromatid
The two identical copies of each
chromosome produced in the S phase are
attached together by centromeres.
Each strand is called a sister chromatid.
http://www.youtube.com/watch?v=VGV3fv-uZYI
http://www.youtube.com/watch?v=C6hn3sA0ip0
Phases of Mitosis
Prophase:
 Chromosomes condense and become visible.
 Nuclear membrane dissolves.
 Centrioles start to migrate to poles
Metaphase:
 Each chromosome (with 2 sister chromatids)
line up along the middle of the “equator”.
 Spindle fibers attach to the centromere of each
chromosome.
Anaphase:
 Centromeres separate (split apart) and sister
chromatids (now each a chromosome) move to
opposite poles.
Telophase/ Cytokinesis:
New nuclei form, chromosomes unwind
back to chromatin.
Cell divides into two new cells.
In plant cells, a cell plate
forms between the two cells.
In animal cells, a cleavage furrow
forms as the parent cell is pinched
into two cells.
Telophase/Cytokinesis:
Telophose has to do with
the nuclei forming around
the two sets of
chromosomes (which are
uncoiling), at opposite
poles of the cell.
Cytokinesis is the process
by which the cytoplasm
divides to form two new
cells.
Actively growing tissue, such as the tip of a
plant root, will have cells undergoing mitosis.
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Identify as many stages as you can in the picture below.
Cancer
Cancer is caused by uncontrolled cell growth
in which cells don’t respond to normal cell
cycle controls, such as contact inhibition.
- Benign growth:
Harmless.
- Malignant growth:
Cancerous
- Metastasis:
Spread of cancer in
the body
Why Cancer Kills
•Since
cancer cells are always undergoing cell
division (mitosis) they do not spend any time in
interphase doing their normal functions.
•They
deprive surrounding normal tissue of
nutrients causing them to die.
•Eventually,
there are not enough healthy, normal
cells in the organ to allow it to function properly.
The Stages of Cancer
Hyperplasia: proliferation of cells (many cells being produced)
Dysplasia: abnormality in maturation of cells, expansion of
immature cells
In Situ Cancer: the tumor is found in the tissue it began in.
Invasive Cancer: the tumor has spread into neighboring tissues.
How does a cell become
cancerous?
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Certain genes (genetic codes) are mutated
(altered) and no longer work properly.
Two types of genes that regulate the cell cycle:
1. Proto-Ocogenes: Promotes cell division (the gas
pedal)
2. Tumor Suppressor Genes: Inhibit cell division (the
brakes)
Proto-oncogenes
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Stimulates cell division
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Produce proteins that signal the cell to divide
– Oncogene: Mutated form of the gene that over
produces the stimulating protein
– The gas pedal is “stuck down”.
Tumor Suppressor Genes
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They inhibit cell division
They produce an inhibitory protein for cell
division
– Mutated genes may not produce the protein
– The brakes “do not work”.