Transcript File

Mitosis is the basis of asexual
reproduction
 It
is necessary for cells to divide,
producing more cells, as an organism
develops.
 Cells die and need to be replaced. Cells
that take a lot of wear and tear, including
skin cells, stomach cells and intestinal
cells need to be replaced.
 The Cell Cycle ensures that body cells are
replaced and the overall health of the
organism is maintained.

Cell Cycle: is a series of three stages in
the life of a cell. The cycle involves
cellular division to produce more identical
cells.

The 3 stages of the Cell Cycle are:
1.
2.
3.
Interphase
Mitosis
Cytokinesis
 Stage
1: Interphase
 Interphase:
is the first and longest stage
of the cell cycle. During this stage the
cell carries out its various functions and
prepares for division.
 During
Interphase the cell doubles all of
its material, including its DNA in
preparing for division. The process of
doubling the amount of DNA in interphase
is called Replication.
 Mitosis:
the second, and usually the
shortest stage of the cell cycle, involves
the division of a cell’s nucleus producing
two identical daughter cells.
 Mitosis
 The
1.
2.
3.
4.
involves 4 distinct stages or steps.
4 stages of Mitosis, in order, are:
Prophase
Metaphase
Anaphase
Telophase

During prophase the double stranded
chromosomes shorten and thicken. The nuclear
membrane that surrounded the nucleus breaks
down and disappears.
 During
metaphase chromosomes line up
across the middle (or equator) of the cell.
 During
anaphase chromosomes are pulled to
opposite ends (poles) of the cell. The
chromosomes are pulled at their centers.

At telophase, the sets of chromosomes that
reached opposite poles form nuclei. They cell is
now ready to divide into two identical daughter
cells.
 Cytokinesis:
is the final stage of the cell
cycle. Once mitosis is complete, the cell
membrane pinches together and the cell
divides into two identical daughter cells.

Mitosis results in one parent cell dividing to
produce two identical daughter cells which have
the same number of chromosomes as the parent
cell.
Think about it …
How many brain cells originally underwent cell
division to produce 24 brain cells?
 A cell divides by mitosis once every two hours.
How many of these cells will be produced after
an 8 hour period?

Special proteins at checkpoints monitor cell
activities and send this information along to the
nucleus.
 At each checkpoint, the nucleus instructs the
cell whether or not to divide.


A cell will stop undergoing division if:
• Not enough nutrients for cell growth
• Replication of DNA did not occur
• DNA is damaged
 Asexual
Reproduction: a method of
reproduction involving only ONE parent,
producing identical offspring to the parent.
 Cloned
organisms are produced through
asexual reproduction.
 Methods
1.
2.
3.
4.
5.
of asexual reproduction include:
Binary fission
Budding
Fragmentation
Vegetative reproduction
Spore formation

Binary fission: a single one-celled parent replicates its
genetic material and divides into two equal parts.

This method is the only method of reproduction for some
types of bacteria.

Amoebas reproduce by binary fission. Algae and protozoa
also reproduce by binary fission.

Budding: part of a cell pushes outward to form
an outgrowth or bud that may detach from the
parent cell.

Unicellular yeasts, and multicellular organisms
such as the hydra and sponges reproduce by
budding.

Fragmentation: a fragment, a piece of an
organism broken off as a result of injury,
develops into a clone of its parent.

Some species of sea stars reproduce asexually by
Fragmentation. Some plants also reproduce this
way.
Vegetative Reproduction: special cells, usually
in plant stems and roots, divided repeatedly to
eventually form a plant that is identical to the
parent.
 Tulips, Daffodils, Potato Sprouts (“eyes”), and
Strawberry stem runners produce plants this
way.




Spore Formation: reproducing asexually by forming single
celled spores.
Spores: a reproductive cell that grows into a new
individual by mitosis. Spores can be carried easily by the
actions of wind and water.
Some plants, including ferns and mosses reproduce by
spore formation. Mold also can reproduce this way.