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Cell Division and Mitosis
Test
Cellular differentiation
• Cell tissues organs organ systems
• As cells grow and divide, many of them may form
tissues inside the body
– Muscle Tissue
• If many tissues group together, they form organs
– Ex: Bicep
• Organ systems are the same as body systems it
is when multiple organs work together to achieve
a common goal
– Ex: Muscular system
Differentiation
• When sperm and egg come together, one cell is
created
• That fertilized egg gives rise to an increased
number of cells through cell division, which must
divide creating identical cells
• As cell division proceeds, cells also undergo
differentiation becoming specialized in structure
and function
• This is done by a process called induction the
use of chemical signals and proteins to alter a
cells DNA to specify or determine its
developmental fate
• Once a cell differentiates-becomes specific cell- it
cannot be reversed
Stem cells
• Stem cells unspecialized cells that
continually reproduce themselves and have,
under appropriate conditions, the ability to
differentiate into one or more types of
specialized cells
• Two types:
– Embryonic-embryos at a very early stage
– Adult- various places in body can be stem cells
• Under appropriate laboratory conditions, stem
cells can differentiate into specialized cells
Drawing
Why do cells divide instead of just get
larger?
• The larger a cell gets, the more demand it puts
on DNA to control the cell (DNA is the same
regardless of size)
• Large cells are not very efficient
• Transport is very difficult
• Cell division makes it easier to dispose of bad
cells
• If you had fewer larger cells, you would lose
large portions of information when a cell dies
Cell division and Mitosis
 If you want to make two batches of cookies
instead of just one, what do you have to do to
the recipe?
Double it
 For a cell to be able to split in two, what does
it need to do?
 Double the “ingredients”
Organelles, DNA, etc.
Vocabulary
 Chromosome one long continuous thread of
DNA that contains many genes
Looks like an “X”
 Chromatin loose combination of DNA, like a
shoe string with knots in it
 Chromatid one half of a duplicated
chromosome
Half of the X
 Centromere junction between two halves
 Centrioles organelle responsible for cell division
 What’s the relationship between a
chromosome and DNA
A chromosome is made up of DNA
DNA twists and folds itself to make a condensed
chromosome
The cell cycle
 Four main stages
 Interphase
G1 (First Gap) cell goes through normal functions
(growth)
Checkpoint-cell must be big enough, mature enough, and have
undamaged DNA
Preparation stage for cell division
Synthesis (S) cell makes a copy of DNA; nucleus now
contains two sets of DNA
G2 (second gap) additional growth-normal functions
Checkpoint
• Mitosis and cytokinesis
Cell splits into two cells
Mitosis and cytokinesis
 In the end, there will be two genetically
identical “daughter” cells
 Interphase G1, S, G2
 Mitosis
Prophase
Metaphase
Anaphase
Telophase
Interphase
• Preparing the cell to
divide
• Growth phase
• DNA duplication
• Cell has two identical
sets of DNA, or
chromatids and is
large enough to
divide
Prophase
 Chromatin condenses
into tightly coiled
chromosomes
 Nuclear membrane
breaks down
 The nucleolus disappears
 Centrioles begin to
migrate to opposite poles
 Spindle fibers-made up
of microtubules begin to
grow from centrioles
form what is called an
Mitotic spindle
Metaphase
• Spindle fibers
attach to
centromere of
each
chromosome
• Chromosomes
line up on the
“middle”
Anaphase
 Chromosomes split,
resulting in two half
sized chromosomes
X splits in half
 Spindle fibers begin
to shorten which
pulls the
chromosomes away
from each other
Telophase
• A complete set of
identical chromosomes
is positioned at each
pole
• Nuclear membrane
begins to reform in each
cell
• Chromosomes begin to
uncoil back into
chromatin
• Spindle fibers fall apart
Cytokinesis In most eukaryotes
• Divides the rest of
the cell into two
pieces
• Actual splitting
process
• A cleavage furrow is
formed from actin
microfilaments
• The filaments start
contracting much
like a drawstring
Cytokinesis in Plant cells
• The difference is in plants, the cell wall must
also divide after telophase
• Cannot form a clevage furrow, instead they
must form a cell plate that enables the cell
wall to divide
The cell cycle control system
• The cell cycle control system allows the cell to monitor
and regulate cell division in order to prevent mistakes
from happening
• Checkpoints critical control point where stop and goahead signals can regulate the cycle
– G1 checkpoint
– G2 checkpoint
– M checkpoint
• External factors
– Cell to cell contact if cells are “bumping” against one
another, cell division will stop until some die to make room for
new cells
– Growth factors protein signals from neighboring cells that
stimulate cell division
• Internal factors
– Apoptosis programmed cell death
Application-Uncontrolled cell division
• Cancers use the process of cell division to
make bad cells multiply without any control
• Transformation when a normal cell changes
into a cancer cell and all regulation stops
– The immune system usually recognizes this and
destroys the cell
• Cancers form disorganized groups of cells
called tumors
Two types of tumors
• Two types:
– Benign non-cancer cells that do not invade
other cells. This usually means that the tumor is
harmless and can be removed
• This person is usually said to not have cancer
– Malignant some of the cancer cells can break
away, or metastasize from the tumor. These cells
can be carried in the bloodstream or in lymph
nodes and can form new cancerous tumors in
other places
• This person is said to have cancer
Carcinogens
• Carcinogen substances known to promote
or produce the development of cancer cells
• Smoking, drinking, drugs, too much of a lot of
things can lead to cancer and apoptosis
• Sometimes your body can detect when there
is a problem
• Ex: skin cells
Treatment for cancer
• Radiation therapy the use of radiation to kill
cancer cells and shrink tumors.
– It works by damaging the DNA of cells so they
cannot divide
– Radiation is localized-its use is targeted to a
specific region-because it can hurt regular cells
• Chemotherapy the use of drugs/poisons to
kill actively dividing cells
On your final sheet to turn in
• Write a good test question on something we
covered today.
• Write down something that you are still
struggling with and need some more
explanation on.
• What was the main idea of the lesson today?
(your answer must be a sentence, not just
mitosis)