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Cell Reproduction--Mitosis
Section 8.2
Why do cells reproduce at all?
Couldn’t they grow really, really big?
• Cells are limited to small sizes, therefore
they must reproduce to make many cells
instead of one big cell.
• 1. Reasons why big cells are bad include:
–Diffusion would be too slow.
–Too many proteins would be needed.
–Cell membrane would not work
properly.
– (surface area of cell) would not be able to
increase as fast as the cell volume)
– (volume = l x w x h; surface area = l x w x 6)
Review: (2) all cells come from
pre-existing cells
• This means that when a cell reproduces or
divides, it creates two cells that are
identical to the original.
• 3. This occurs not only because it
is better to have many small cells,
but also because
• an organism needs to grow or
replace dead tissue. (growth and
to replace dead tissue
• Results in population growth in
unicellular (one-celled)organisms.
4. Chromosomes are structures
that carry the coiled DNA.
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5. Chromosome
• Centromere—hold together the
halves
Sister chromatid
(the two halves
of a replicated
chromosome)
The Cell Cycle
• 6. The cell cycle is the steps a cell
goes through during its life.
•.
7. a. interphase
• A. interphase--a period of
growth and DNA replication.
• Most of a cell’s life is spent in this
stage
Interphase
The stage where the cell grows and does normal stuff
This is also where your DNA replicates
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
7.b. Mitosis
• B. Mitosis-- cell
division resulting
in 2 identical cells
• There are a series of steps after
which 2 identical cells are formed,
each with complete set of
chromosomes.
8. Steps of Mitosis (PMAT)
•
•
•
•
Prophase--prepares
Metaphase--middle
Anaphase--apart
Telophase--two
• **use the terms to provide clues for what
happens in each step**
Directions for diagrams:
• You will cut out descriptions for what
occurs during the 4 steps of mitosis. As
you read through the next slides, you will
match the description with the diagram on
your paper and glue or tape it down in the
box provided.
• First and longest step.
• Chromatin (DNA) coils
into chromosomes.
.
• nuclear membrane
disappears.
• In animal cells, centrioles
and spindle fiber have
formed
Prophase
The 1st step of Mitosis,,,,,,Prophase
DNA thickens into
chromosomes
Nuclear membrane
disappears
Centrioles move to poles of cell and make
spindle fibers
Animal Cell
Plant Cell
Spindle fibers
Centrioles
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Metaphase
• Chromosomes attach
to the spindle fibers at
the centromere.
• chromosomes line
up in the middle of
the cell, so each
sister chromatid is
facing a pole.
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Anaphase
• Sister
chromatids are
pulled apart
towards opposite
poles.
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Telophase
• Chromatids reach
opposite poles and
begin to uncoil.
• Two new nuclei are
formed.
• new cell membrane
begins to form
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
10. Cytokinesis….this is when the cell
actually splits in two and divides the
cytoplasm in half
In animal cells it
pinches in two this is
called a Cleavage
Furrow
• Cell membrane moves inward to create two
daughter cells – each with its own nucleus
with identical chromosomes.
Cytokinesis In plants the cell just builds a
new cell wall straight down the middle
Animal Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Plant Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
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• http://207.207.4.198/pub/flash/8/8.html
http://www.cellsalive.com/mitosis.htm