Transcript 5.5 Stages of Mitosis Notes & Questions

5.5
Reproduction and Cell Division
Reproduction
and Cell Division
 The Cell Cycle and Mitosis
The Cell Cycle
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Division Phase:
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Prophase
Metaphase
Anaphase
Telophase
Interphase
What is and is not Mitosis?
Mitosis is nuclear division plus
cytokinesis, and produces two identical
daughter cells during prophase,
metaphase, anaphase, and telophase.
Interphase is often included in
discussions of mitosis, but interphase is
technically not part of mitosis.
Interphase
The cell is engaged in metabolic activity
and preparing for mitosis (the next
four phases that lead up to and
include nuclear division).
Chromosomes are not clearly discerned
in the nucleus, although a dark spot
called the nucleolus may be visible.
The cell prepares for cell division by
duplicating its genetic material.
Prophase
Chromatin in the nucleus begins to
condense and becomes visible in
the light microscope as
chromosomes.
The nucleolus disappears.
Centrioles begin moving to opposite
ends of the cell and fibers
extend from the centromeres.
Some fibers cross the cell to form
the mitotic spindle.
Metaphase
Spindle fibers align the
chromosomes along the middle of
the cell nucleus.
This line is referred to as the
metaphase plate.
This organization helps to ensure
that in the next phase, when the
chromosomes are separated, each
new nucleus will receive one copy
of each chromosome.
Anaphase
The paired chromosomes separate
and move to opposite sides of the
cell.
The two halves move to opposite
poles of the cell.
If anaphase proceeds correctly,
each of the daughter cells will
have a complete set of genetic
information
Telophase
Chromosomes arrive at opposite
poles of the cell, and new
membranes form around the
daughter nuclei.
The chromosomes disperse and are
no longer visible under the light
microscope.
The cytoplasm and organelles
separate into roughly equal parts,
and the two daughter cells are
formed.
Cytokinesis
In animal cells, cytokinesis results when a
fiber ring composed of a protein called
actin around the center of the cell
contracts, pinching the cell membrane in
the middle and forming two new
daughter cells.
In plant cells, the rigid wall requires that
a new cell wall forms along the middle,
creating two new cells.
Reproduction and Cell Division
Reconsider the modern cell theory:
 All living things are made up of one or more
cells.
 The cell is the functional unit of life.
 All cells come from pre-existing cells.
Cell division, the process by which cells come
from pre-existing cells, is the process that
perpetuates life and allows species to
continue.
Just as cells reproduce as part of the cell cycle,
living organisms reproduce as part of their
life cycle.
Note that some organisms use both
methods of reproduction. For example,
bacteria reproduce mostly in an asexual
process called binary fission, which is
basically cell division as you have
learned it. However, bacteria are also
able to exchange genetic information in
a form of sexual reproduction.
Similarly, most plants reproduce sexually,
in the process that results in seeds, but
many also reproduce asexually in various
other ways.
Reproduction of Cells
Questions
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P.153 #2,3,5 and 6