Download Mitosis and Meiosis

Mitosis and Meiosis
Mitosis and Cytokinesis
Biology
Fall 2012
Objectives
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Summarize the events of the four stages of mitosis
Differentiate cytokinesis in animal and plant cells
Bell Ringer
What do you think the following prefixes mean?
1.
A.
B.
C.
D.
2.
ProMetaAnaTelo-
How does a cells ATP use change during mitosis?
Bell Ringer
What do you think the following prefixes mean?
1.
A.
B.
C.
D.
Pro- “earlier than”
Meta- “later than, or after”
Ana- “up or back”
Telo- “end”
How does a cells ATP use change during mitosis?
2.
1.
The events of mitosis require a lot of additional energy, which
is supplied by ATP
Chromatid separation in Mitosis
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Last two phases of the cell cycle:
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Mitosis and cytokinesis
Chromatid separation in Mitosis
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Mitosis: nucleus divides to form two nuclei each containing
a complete set of the cells chromosomes
Cytokinesis: cytoplasm is divided between the two
resulting cells
Chromatid separation in Mitosis
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During mitosis chromatids are physically moved to opposite
sides of dividing cell with help of spindle
Spindle: cell structures made up of both centrioles and
individual microtubule fibers that are involved in moving
chromosomes during cell division
Forming the Spindle
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Centrosome: organelle that organizes the assembly of the
spindle
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At each of cells poles
In animal cells a pair of centrioles are found in each
centrosome
Forming the Spindle
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Centrioles and spindle fibers are made of hollow tubes
of protein
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Called microtubules
Spindle fibers made of individual microtubules
Centrioles made of 9 triplets of microtubules arranged in a
circle
Forming the Spindle
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Plant cells DO NOT have centrioles
Form a spindle that is almost identical to that of an animal
cell
Separation of Chomatids by
Attaching Spindle Fibers
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Two sets of microtubules extend out toward opposite poles
Once microtubules attach to the centromeres and poles,
the two chromatids in each chromosome can be separated
Separation of Chomatids by
Attaching Spindle Fibers
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Paired chromosomes separate
One of the pair of chromatids will move
to one of the poles of the cell
The second member will move to the
other pole
Chromatids draw closer to the poles of
the cell as these microtubules are
broken down bit by bit and become
shorter
Mitosis

Step #1: Prophase
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
Chromosomes coil up and become visible
Nuclear envelope dissolves and a spindle forms
Mitosis

Step #2: Metaphase
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Chromosomes move to the center of the cell
Line up along equator
Spindle fibers link chromatids of each chromosome to opposite
poles
Meta =
middle
Mitosis

Step #3: Anaphase
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
Centromeres divide
Two chromatids (now called chromosomes) move toward
opposite poles as the spindle fibers attached to them shorten
Mitosis

Step #4:Telophase
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Nuclear envelope forms around the chromosomes at each pole
Chromosomes now at opposite poles uncoil and spindle
dissolves
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Mitosis complete!
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Cytokinesis
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Cytoplasm of cell is divided in half
Cell membrane grows to enclose each cell, forming two
separate cells
Cytokinesis
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In animal cells:
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Lack cell walls
Cell is pinched in half
Cytokinesis

In plant cells:
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Have cell walls
Form a cell plate
Cell plate: membrane bound cell wall that forms across the
middle of the plant cell
New cell wall then forms on both sides of cell plate, separates
the plant cell into two new cells
Cytokinesis
Cytokinesis

Animal Cell

Plant Cell
Review
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White boards:
Draw prophase
Draw metaphase
Draw anaphase
Draw telophase
Draw cytokinesis in plant cells
Draw cytokinesis in animal cells