MITOSIS
•Mitosis is a cell division or cell cycle process which
results in two daughter cells having the same
number and kind of chromosomes as the parent cell.
Mitosis and cytokinesis result in cell division, or the
production of two new daughter cells.
Why is Mitosis Important?
Why does it occur?
1.
2.
At some point in a cell’s life, it grows to
such a size that the processes that go on in
the cell become less efficient, the distances
too great for the chemical messages to
travel, and the cell simply becomes less
efficient.
New daughter cells are required for
growth and repair of cells, reproduction
and replacement of dying cells.
Phases of Mitosis
1.Interphase:
The longest phase in which the cell is dormant except for the
dispersion of chromosomes.
2.Prophase:
First stage of Mitosis where the chromosomes compact themselves
from dispersed chromatin.
3.Metaphase:
Second stage of Mitosis where the chromosomes line up in the
middle of the cell perpendicular to the poles.
4.Anaphase:
Third stage of cell division when the chromosomes begin to divide
into two sister chromatids and go to opposite ends of the cell.
5.Telophase & Cytokinesis:
Final stage where the cytoplasm divides completely in to two, the
nuclear envelopes reform, and the nuclei begin to reform resulting
in two new cells.
Interphase- Stage 1
The period between successive nuclear
divisions during which the
chromosomes are NOT VISIBLE and
the nuclear envelope is intact.
3 things occur
1.
During the first part of interphase
(G1) the daughter cell gets more
energy and becomes larger.
2.
After the cells have enough energy
and their size is large enough, they go
through the S-Phase. In this phase the
nuclear material duplicates.
3.
Since the S-Phase took so much out of
the cell, it has to go through the G2
phase. In this phase the cell becomes
large again and receives more energy
(like the G1 phase). This energy that is
made in G2 is used in cell division of
mitosis.
Prophase – Stage 2
•Chromatin condenses to
form chromosomes.
Nucleolus reduced and
finally disappears.
•Nuclear membrane
disappears
Prophase (cont’d)
•Mitotic spindles form; these are
also called Astral rays and they
connect the centromere to the
poles.
•The Spindles extend from the
pole to the equator and are
needed to align the
chromosomes at metaphase, for
pole movement and separation
of the daughter nuclei.
Metaphase – Stage 3
•The Nuclear envelope breaks down.
•Spindle moves into nuclear region
and vesicles occupy nuclear region
•Chromosomes attach to the spindle
and move to the midpoint
•Chromatids align to opposite poles
Anaphase – Stage 4
The centromere divides and
the chromatids of each
chromosome are pulled apart
to their respective sides of the
spindle.
Telophase- Stage 5
•The final stage in mitosis is
telophase.
•The two separated groups of
chromosomes (located at
opposite ends of the spindle
after their separation in
anaphase) finally totally pull
apart.
Telophase- Stage 5, cont’d
•Each group of
chromosomes forms a
nuclear envelope around
themselves, creating two new
cells.
•The chromosomes uncoil
until they resume the form
of random, tangled
chromatin (as is in
interphase.) The splitting of
one cell into two is now
complete.
Cytokinesis
This process usually follows
directly after mitosis.
•In animal cells, the cells
finally separate by
"furrowing" the membrane
with an "invisible thread" of
action and myosin- separating
the two cells.
•In plant cells, a cell plate
forms between the two dividing
cells, which will eventually
become the two new cell walls.
•After the process is complete,
both daughter cells contain all
the properties of a complete,
functioning