Download Mitosis

Chapter 6 Section 3
MITOSIS AND CYTOKINESIS
Grade 10 Biology
Fall 2010
Objectives
 Describe the structure and function of the spindle
during mitosis
 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.
ProMetaAnaTelo-
2. 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”
2. How does a cells ATP use change during mitosis?
1.
The events of mitosis require a lot of additional energy,
which is supplied by ATP
Chromatid separation in Mitosis
 Last two phases of the cell cycle:
 Mitosis and cytokinesis
Chromatid separation in Mitosis
 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
 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
 Centrosome: organelle that organizes the assembly
of the spindle

At each of cells poles
 In animal cells a pair of centrioles are found in
each centrosome
Forming the Spindle
 Centrioles and spindle fibers are made of hollow
tubes of protein

Called microtubules
 Spindle fibers made of individual microtubules
 Centrioles made of 9 triplets of microtubules
arranged in a circle
Forming the Spindle
 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
 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
 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
 Chromosomes coil up and become visible
 Nuclear envelope dissolves and a spindle forms
Mitosis
 Step #2: Metaphase
 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
 Centromeres divide
 Two chromatids (now called chromosomes) move toward
opposite poles as the spindle fibers attached to them shorten
Mitosis
 Step #4: Telophase
 Nuclear envelope forms around the chromosomes at each pole
 Chromosomes now at opposite poles uncoil and spindle
dissolves

Mitosis complete!
Cytokinesis
 Cytoplasm of cell is divided in half
 Cell membrane grows to enclose each cell, forming
two separate cells
Cytokinesis
 In animal cells:
 Lack cell walls
 Cell is pinched in half
Cytokinesis
 In plant cells:
 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
 White boards:
 Draw prophase
 Draw metaphase
 Draw anaphase
 Draw telophase
 Draw cytokinesis in plant cells
 Draw cytokinesis in animal cells