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The Cell Cycle
I need a volunteer!
• Does anyone have a mirror?
• Take it out and let me call on you to come
up to the class
• I want to see how my hair is …or do I?
• After reading about mitosis for homework,
you should be able to explain this
sentence:
In biology division is the same thing as
multiplication.
Differentiation
How does one cell become
not just many cells, but
specialized cells, such as
heart cells, brain cells, ear
cells, stomach cells, etc?
This is due to differentiation.
At the earliest stage of life,
cells are unspecialized, but
the DNA inside of them
causes them to differentiate,
which means they become
specialized- each with a
different function.
Mitosis
We all started off as a tiny, single cell. That
cell then underwent a process called
mitosis (cell division)which then created
another cell identical to it.
After fertilization occurs, mitosis
begins
A baby slowly grows into an adult
This is a result of cells dividing to make
more cells.
Mitosis involves somatic cells
Somatic Cells
All body cells are
somatic cells- these
cells undergo mitosis
and are diploid which
means they have 46
chromosomes.
Gamete Cells
Sperm and egg cells
are gamete cellsthese cells undergo
meiosis and are
haploid which means
they have 23
chromosomes.
Cell Cycle
The cell cycle is the regular sequence of
growth and division that cells
undergo.
The cell cycle has three parts: interphase
mitosis
cytokinesis
Chromosome
• Chromosomes, which contain DNA, are
found inside the nucleus in the cell
Cells divide to make specialized cells, which make
up tissue, which make up organs=organism
Interphase
• The first stage of the cell cycle
• It is the period before cell division
During interphase three things happen:
• The cell grows to its mature size
• It makes a copy of its DNA and organelles
• It prepares for mitosis
The cell spends most of its time in interphase. Mitosis takes about an
hour to complete. Some cells divide every 24 hours. Cells must wait for
a chemical signal before moving on to each phase of the cycle.
Mitosis
• Mitosis consists of four phases, prophase,
metaphase, anaphase, and telophase
• Mitosis is the process by which a cell’s
nucleus divides to create a daughter cell
that is genetically identical to the parent
cell
• It occurs in somatic cells only
• We call the original cell the parent cell and
we call the new cell a daughter cell
When do your cells undergo
mitosis?
• When healing injured tissue
• During growth- zygote to adulthood
• Regular maintenance of the body
For example, stomach cells are in a harsh,
acidic environment so they do not live very
long and are replaced every few days by
new cells through mitosis.
Prophase
• The nuclear membrane begins to break
down
• The chromatin in the nucleus begins to
condense and coil, like fishing line around
a ball (becoming chromosomes)
• Since DNA has replicated in interphase,
each rod has doubled, each being an
exact copy of the other
• Spindle fiber forms from the centrioles
Prophase
Metaphase
The
chromosomes
line up across the
center of the cell
Each
chromosome
attaches to a
spindle fiber at
its centromere,
which holds the
chromatids
together
Metaphase
Metaphase
• Chromosomes move along the spindle
fibers and line up at the equator of the cell
Anaphase
The centromeres
split
The two
chromatids
separate
Each chromatid
moves along the
spindle fiber to
opposite ends of
the cell
The cell stretches
out
Anaphase
• Chromosomes begin to pull apart and
move to opposite ends of the cell
Telophase
• The chromosomes begin to stretch out
and lose their rod like structure
• This occurs in two regions at the ends of
the cell
• A new nuclear membrane forms around
each chromosome
Telophase
A Summary of Mitosis
Cytokinesis
• The cell membrane pinches in around the
middle of the cell, eventually splitting in
two
• Each daughter cell ends up with the same
number of identical chromosomes and
about half of the organelles and cytoplasm
Cytokinesis
Division of the cytoplasm and organelles
Cytokinesis
Plant cell cytokinesis
• A plant cell does not divide in the same
way as the animal cell because its cell wall
is too rigid to squeeze together the way
the animal cell does
• Instead a cell plate forms in the middle of
the cell (made of sticky carbohydrate)
• The cell plate gradually develops into a
cell membrane, then a cell wall develops
Plant Cell Cytokinesis
Note Check
1. What are the three phases of the cell
cycle?
2. What are the four phases, in order, of
mitosis?
3. In which phase does DNA replicate?
4. In your own words what is mitosis?
5. Why are the daughter cells genetically
identical to the parent cell in mitosis?
Cancer
• Any substance that is known to cause
cancer is called a carcinogen
• Cancer can be caused by genetic factors,
environmental factors, and /or a unhealthy
diet
• Cancer occurs when a mutation occurs in
the DNA
• The cell no longer follows the “check point
rules” of the cell cycle
Cancer
• Cancer cells can be thought of as “bully” cells,
they don’t play by the rules
• They divide uncontrollably, invading the space of
other cells so that they no longer can survive
• A tumor results from a mass of cells
• Benign tumors are “good” because they are
localized and are easy to remove
• Malignant tumors are “bad” as they are able to
spread throughout the body and are more
difficult to treat
What phase am I?
What phase am I?
• Metaphase!
Which phase am I?
Anaphase!
How about me?
Which Phase am I ?
Telophase!
And what phase am I in?
Cell Cycle Quiz
1. The three parts of the cell cycle, in order
are:
a. interphase, mitosis, cytokinesis
b. Mitosis, interphase, cytokinesis
c. Cytokinesis, interphase, mitosis
d. None of the above
2. The process by which cells divide and
make cells with identical chromosomes is
called:
a. Interphase
b. Meiosis
c. Mitosis
d. centromere
3. What phase of mitosis am I
in?
4. Sister chromatids (identical
chromosomes) attach to________at their
centromeres.
a. Spindle fibers
5. The identical cell created as a result of
mitosis is called a_______.
a.
b.
c.
d.
Son cell
Parent cell
Lovely cell
Daughter cell