Download - Cancer and Cell Differentiation
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Cancer and
Cell
DifferentiationHomework:
Page 37 #10, 12, 14, 17, 18
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Recall
The cell cycle consists of interphase, mitosis, and
cytokinesis.
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Recall
During S phase of interphase, the DNA is replicated
to prepare for mitosis. Each daughter cell must have
a nucleus containing genetic information that is
identical to that that was in the parent cell.
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Cell Cycle Checkpoints
During this process of DNA replication, or at other
times during the cell cycle, ‘mistakes’ can be made
in the sequence of nucleotides in DNA (similar to a
typo in a sentence or word).
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Cell Cycle Checkpoints
Depending on the severity of the error, this could
cause large problems for the cell if it is not able to
be repaired before it is passed on to subsequent
cells.
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Cell Cycle Checkpoints
To prevent these errors from being passed on, cell
cycle checkpoints involve proteins that make sure
the DNA is replicated correctly to divide.
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Cell Cycle Checkpoints
Cell division happens at different rates for different
cells but cells will not continue to undergo mitosis
forever.
If cells suffer irreparable damage, they will undergo
cell necrosis. Sometimes cells will undergo a
controlled death known as apoptosis.
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Tumour Formation If the errors in the DNA sequence affect the
components that control the cell cycle, it could
lead to uncontrolled cell division and growth of
functionless cells.
This could lead to tumour formation and cancer.
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Tumour Formation
A benign tumour does not harm other surrounding
tissues. However, a malignant tumour will interfere
with the functioning of surrounding cells. This is the
tumour type associated with cancer.
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Mutations and Cancer
The changes in the
DNA sequence are
known as mutations.
Depending on the
type of change, they
may have no effect,
a positive effect,
or a negative effect.
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Mutations and Cancer
Multiple mutations with different effects can also
build upon one another to eventually have a
compounded effect.
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Mutations and Cancer These changes in DNA can be random but there
are also certain environmental factors that can
increase the likelihood of mutation. These are
known as carcinogens.
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Mutations and Cancer
Other factors, such as genetics, can also contribute
to the likelihood of developing cancer.
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Zygote Formation
When a sperm and an egg cell fuse together, they
form a zygote. This is the single cell that will give rise
to the rest of the cells through mitosis.
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Zygote Formation However, if mitosis produces identical cells, how do
we get all the different types of cells in a
multicellular organism?
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Cell Differentiation
A specialized cell is a cell that has a specific
structure and function. Cellular differentiation is the
process by which a cell becomes specialized to
perform a specific function.
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Cell Differentiation
The following are three factors that can influence cell
specialization in animals:
1. Cytoplasm Contents
The contents of a cells cytoplasm differs within
each newly divided cell
e.g. differing amounts of organelles are present in
different types of cells
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Cell Differentiation
2. Environmental Conditions
External factors such as temperature, pressure,
and nutrient availability can affect the
specialization of cells
e.g. hair colour development in cats that differ
based on temperature of the environment
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Cell Differentiation
3. Neighbouring Cell Secretions
Secretions from neighbouring cells can influence
cell specialization
e.g. embryonic development or regeneration
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Regeneration
Regeneration is the process whereby a body part is
replaced or regrown.
Different organisms have different levels of
regeneration potential. For example, humans can
regenerate parts of the liver whereas salamanders
can regenerate full limbs.
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Stem Cells
A stem cell is an
undifferentiated cell.
When they zygote is
formed, it can be
considered a totipotent
stem cell, which have the
ability to differentiate into
any cell type.
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Stem Cells
During embryonic development, cells become
pluripotent stem cells. These cells can still
differentiate into any cell type in the body but not
the placenta for the embryo.
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Stem Cells
As these pluripotent cells become more specialized,
they become multipotent stem cells which can only
develop into a few specialized cells within a certain
tissue type.
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Uses for Stem Cells Early embryonic stem cells are considered to be
totipotent or pluripotent. Adult stem cells are
considered multipotent.
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Uses for Stem Cells Blood found in the umbilical cord after birth can
also be a source of multipotent stem cells. Parents
may have the option to bank the cord blood for
future emergencies because these cells are able to
differentiate into different types of blood cells.
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Uses for Stem Cells Stem cells found in plants are known as
meristematic cells. Cuttings from plants including
these cells can regenerate the whole plant.
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Uses for Stem Cells
For example, leukemia is a cancer that affects
white blood cells. Traditionally, chemotherapy
destroys the diseased cells before they are
replaced with healthy bone marrow from a donor.
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Uses for Stem Cells
However, stem cells from umbilical cord blood can
also be used as they can differentiate into different
types of blood cells.