Download The Cell Cycle

Chapter 9:
The Cell Cycle
Section 1
Chromosomes are the structures
that contain genetic material that
is passed on from generation to
generations of cells.
Chromatin is the relaxed form of
DNA in the cells nucleus.
Recap! You guys read last
week about cell size and the
limitations to this.
Can anyone tell me what
they remember from the
reading?
Once a cell reaches its size limit it will
either die or divide.
*Cellular
division is the
way a cell
reproduce as
well
Cell reproduction by a cycle of growing
and dividing is called the Cell cycle.
Each time a cell goes through one complete
cycle, it becomes two individual cells. When,
repeated over and over again! millions of new
cells are made!
There are three main stages of the
cell cycle.
Interphase, the stage
in which the cell grows,
carries out cellular
function, and replicates,
or makes copies of its
Genetic material (DNA)
in preparation for the
next stage of the cell
cycle.
Interphase is
subdivided into
three groups;
𝐺1 , 𝑆 𝑎𝑛𝑑 𝐺2
During 𝐺1 , the
cell grows and
carries out
normal cellular
function in
preparation to
replicate DNA
(genetic
material).
During the S
phase, the cell
copies its DNA in
preparation for
cell division.
The 𝐺2 stage is the
period when the cell
prepares for the
division of its nucleus.
The cell also takes
inventory at this time
and makes sure it is
ready to continue with
Mitosis. If it passes this
check point it will go
on.
Mitosis, the stage of
the cell cycle during
which the cell’s
nucleus and Nuclear
Material divide and
separate to opposite
ends of the cell.
* Mitosis itself is
subdivides into four
stages.
At the end of
mitosis, Cytokinesis
begins.
•Cytokinesis is the
method by which a
cell’s cytoplasm
divides, creating
two identical cell.
How long does this process take?
• Time of the cell cycle
depends on the type
of cell. Some
Eukaryotic cells take
up to 8 minutes, while
other cells might take
up to a year.
• For most normal cells,
it takes about 12-24
hours for this process
to be carried out.
Mitosis and
Cytokinesis
Section 2
RECAP!
•Yesterday we talked about the cell cycle.
We went over how cells go through
interphase (𝐺1 , 𝑆, 𝐺2 ), Mitosis, and
Cytokinesis.
•During interphase, the cell is growing,
replicating the DNA within the nucleus,
and Preparing to split the nucleus to
move on to the other phases.
•During Mitosis, the cell’s replicated
DNA and the cell prepares to
separate into two cells.
•During Cytokinesis, the cell’s
cytoplasm divides creating two
identical daughter cells.
Mitosis
•The key activity for mitosis is the
accuracy in the separation of the
cell’s replicated DNA.
•This allows the genetic information
to pass on to the new cells, resulting
in two identical Daughter cells.
• Each half of the X is
called a sister
chromatid.
• Each structure contains
identical copies of DNA.
• The structure at the
middle of the
chromosome is called a
centromere.
In Multicellular organisms, such as
ourselves, Mitosis increases the
number of cells as a young organism
develops into its adult size.
Organisms also use mitosis to replace
damaged cells.
Think back to the last time you
scraped your knee or got a cut.
• Your body’s healing process
involves creating new skin
cells from your already
existing cells.
Under your scab, your existing skin cells
will divide my mitosis and cytokinesis,
creating new skin that will fill the gab
caused by your cut.
Reflect back to
yesterday!
Mitosis occurs
after interphase
has completed.
Stages of Mitosis
Mitosis is Divided into Four Stages
Prophase
Metaphase
Anaphase
Telophase
*A good way to remember
these Stages in order is to
remember P-MAT
Prophase
• This is the First and longest stage of mitosis.
• In this stage the cells Chromatin tightens into
chromosomes (shaped like an X).
• As prophase continues
• The nucleus disappears
• Microtubule structures called spindle
fibers form in the cytoplasm.
• Centrioles migrate to the ends of the cell.
• Coming out of the centrioles are a type of fiber
called aster. (creates the star like appearance)
• The whole entire structure (spindle fibers,
centrioles , asters) is called The Spindle
apparatus.
• This structure is important for the moving and
organizing of the chromosomes for Division.
At the end of prophase:
• The nuclear envelope disappears.
• The spindle fibers attach to the sister
chromatids of each chromosome on both sides
of the cell.
Metaphase
• During metaphase, the sister chromatids are
pulled by motor proteins along the spindle
apparatus toward the center of the cell and they
line up in the middle.
• This is one of the shortest stage of mitosis but
one of the most important for it insures that the
chromosomes have been copied accurately.
Anaphase
• During anaphase, the chromosomes are pulled apart
• The microtubules of the spindle apparatus become
shorter, therefore pulling the sister chromatids apart.
Separating them into identical chromosomes.
• At the end of anaphase, the chromosomes will be
completely pulled to the opposite ends of the cell.
Telophase
• Chromosomes reach
the poles (ends) of the
cell.
• Nuclear envelope reforms.
• Nucleus reappears
• Chromosomes relax
back into chromatin.
Cytokinesis
Recall from
yesterday that
this occurs at
the end of
mitosis.
Cytokinesis
•In a plant cell:
• Cell plate forms
dividing daughter
cells
•In an animal cell:
• Cleavage furrow
forms an equator of
cell and pinches
inward until cell
divides into two.
1. What is a centromere?
2. What is half of a chromosome
called?
3. Where are the chromosomes
located during Metaphase?
4. What is the acronym for
mitosis?
5. After what stage of the cell
cycle does Mitosis occur?