Transcript chromosome - Toolbox Pro

Mitosis
CELL
DIVISION
DURING MITOSIS
The cell nucleus divides into
two identical halves. These
halves contain the same number
of chromosomes as the parent
cell.
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Chromosome – A double rod
shaped structure that contains
DNA and protein.
CHROMOSOME
Threadlike strands of
DNA and protein in a
cell nucleus that carry
the code for the
inherited
characteristics of an
organism.
Please draw this and label.
Two identical sister
chromatids make up a
single chromosome.
These chromatids are
held together by a
centromere.
Dividing the Information
When a cell divides, it
must also divide its
genetic information so that
it can perform all the
activities of the parent
cell.
Mitosis is a Process
Mitosis is divided into a
series of specific steps or
phases that are part of the
division process. Each
phase involves significant
phenomenon with specific
events occurring.
INTERPHASE
During interphase the chromosomes are not
visible. Amazingly, during this phase the
genetic material is making an identical copy
of itself. This process is called replication.
It is this process of replication that allows
chromosomes to remain double stranded,
generation after generation.
INTERPHASE
The cell to the left is in interphase.
Note that the two green objects near
the top are called centrioles. The
large outer circle is the cell
membrane. The smaller gray circle
is the nuclear membrane(covering of
the nucleus). The orange-pink fiberlike material is the chromatin. In a
later phase, this chromatin will
eventually organize into
chromosomes.
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Interphase:
1. DNA is replicating (making
copies of itself)
2. Organelles are replicating.
3. Nucleus is visible.
4. Genetic information appears
as chromatin.
PROPHASE
During prophase, chromosomes
become fully visible. The nucleolus
and the nuclear membrane disappear.
The centrioles begin to migrate out
towards opposite ends of the cell. Thin
thread-like fibers called spindle fibers
begin to stretch across the cell.
PROPHASE
Observe that the centrioles are
moving out toward the poles of the
cell. The material in the nucleus is
becoming more condensed so that
chromosomes may form. A series of
threads will begin to stretch from the
centrioles toward the chromosomes.
These threads make up the spindle
apparatus.
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Prophase
1.
2.
3.
Chromatin bunches up to form
chromosomes.
Nuclear envelope disappears.
Centrioles appear in animal
cells to aid in division. They
begin moving to the poles.
METAPHASE
In metaphase, the chromosomes line up along a central
line known as the equator or equatorial plate. The
spindle apparatus attaches to the centromere of each
chromosome. The centrioles have moved to the poles
(outer ends) of the cell.
METAPHASE
Take note of the fact that the nuclear
membrane is not present. The
chromosomes are lined up on the equator
of the cell and the centrioles are attached
to the centromeres of each chromosome
using the thread like structures called
spindle fibers.
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Metaphase
1.
2.
3.
Chromosomes line up at the
equator.
Spindle fibers are attached.
Centrioles are at the poles.
ANAPHASE
In anaphase, the chromosomes are
pulled apart by the spindle fibers. This
divides the genetic material(DNA) into
two identical halves. One chromatid of
each chromosome will end up in each
half of the dividing cell.
ANAPHASE
Notice that the chromosomes
have been ripped into two
separate halves. These
chromatids are being pulled out
towards the centrioles near the
poles.
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Anaphase
1. Chromosomes get pulled apart
so that one chromatid will go
toward each pole.
TELOPHASE
The final step to mitosis is telophase. During this step the
centrioles and spindle fibers begin to disappear. The
chromosomes begin to spread out and are harder to see. The
nuclear membrane and a nucleolus begin to reappear in each
newly formed half. The cell membrane pinches off so that each
newly formed cell can separate.
TELOPHASE
Observe that two separate cells exist
by the end of telophase. This occurs
when the cell membrane pinches off
and separates. In plant cells, a cell
plate forms in the middle to separate
the two cells. The nuclear
membrane has appeared and the
chromosomes are no longer
organized. These two new cells are
called daughter cells.
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Telophase
1.
2.
3.
Cell membrane pinches inward
to divide up the cytoplasm and
cell membrane.
Nuclear envelope reappears.
By late telophase the
chromosomes begin to
unbunch to appear as
chromatin.
REMEMBER
Mitosis is the process of a cell’s nucleus dividing
in two. When the process is complete, the two
new cells are identical to the parent with the same
number of chromosomes as the parent.
What’s it really look like?
The following are pictures
of real cells at various
stages of mitosis.
INTERPHASE
Clearly a nuclear
membrane present and
the chromosomes are
not visible. This is an
animal cell.
INTERPHASE
The same is true in the
plant.
PROPHASE
In prophase the nuclear
membrane begins to
disappear and the
chromosomes begin to
organize.
PROPHASE
It is very much the
same in the plant cell.
METAPHASE
In metaphase the
spindle apparatus forms
and attaches to the
chromosomes, which
have moved to the
center.
METAPHASE
The center line of
the cell is called the
equator or
equatorial plate.
ANAPHASE
In anaphase the
chromosomes are
split in half and each
half is pulled towards
the poles.
ANAPHASE
This divides the genetic
material into two identical
halves.
TELOPHASE
By the end of
telophase two
daughter cells have
been created and all
cellular organelles are
divided.
TELOPHASE
In plant cells, there is a
cell wall that keeps them
from bending in. As a
result, a cell plate is
formed down the middle
to complete the cell’s
covering.
How long does it take?
The time for division varies
from cell to cell. To the right a
type of cell that divides about
every 16 hours is shown. Note
that much of the time is spent
growing(g1 and g2) and creating
a copy of the DNA(s). Only
one of the 16 hours is actually
spent dividing.
Above, is a time line showing how long each
stage of division may take. Cytokinesis is the
time that the cell is actually dividing organelles
and the membrane.
That’s
how
cells
divide!
IT’S TIME TO
TAKE SOME
NOTES AND
DRAW A
DIAGRAM.
Draw the following
diagrams into your notes.
Be sure to label the parts.
INTERPHASE
IMPORTANT POINTS:
•The nuclear membrane is visible.
•The nucleolus is visible.
•Genetic material is difficult to see
and called chromatin.
•Centrioles are near each other.
•DNA is replicated(copied).
PROPHASE
IMPORTANT POINTS:
•Chromosome appear
•Centrioles begin to migrate to
the poles.
•Chromosomes consist of two
sister chromatids.
METAPHASE
IMPORTANT POINTS:
•Spindle apparatus is
completely formed.
•Chromosomes line up at the
equator (equatorial plate)
•Centrioles at the poles.
•Nuclear envelope and
nucleolus gone
ANAPHASE
IMPORTANT POINTS:
•Chromosomes are being pulled
apart by spindle apparatus.
•Chromatids move towards the
poles.
TELOPHASE
IMPORTANT POINTS:
•Cell membrane pinches into two
separate cells.
•Nuclear membrane reappears.
•Two new daughter cells are created
that are genetically identical.
PLEASE LET YOUR
TEACHER KNOW
YOU ARE DONE!