MITOSIS
AND
CYTOKINESIS
Cell Reproduction
• Cell division
– - process by which new cells are produced from
one cell
– - Mitosis - produces 2 cells identical to parent cell
The Cell Cycle
• - the sequence of growth and division of a cell
• - a cell’s life cycle from origin to division
2 major periods
• Interphase
• Cell division
G1
S
G2
Interphase
G1 phase-• Cell grows, produces many proteins, functions
• Chromatin present, not coiled, chromosomes
not visible, nucleus looks grainy, nucleolus
visible
Interphase
Rapid
growth
and
metabolic
activity
S Phase--DNA replication – copies chromosomes
Interphase
DNA synthesis
and replication
G2 phase --• - mitochondria and centrioles double
S
Interphase
G1
G2
Centrioles replicate; cell
prepares for division
• Cell Division Phase
–Mitosis
–Cytokinesis
S
Interphase
G1
G2
Mitosis – 4 phases
Cytokinesis
Mitosis---•Prophase
•Metaphase
•Anaphase
•Telophase
Intro to Mitosis
1:51
Eukaryotic chomosomes
Prophase: The first phase of mitosis
• - Chromatin coils and condenses
• - Chromosomes become visible
• Centrioles in centrosomes
Spindle fibers form
– from centrioles
Nuclear membrane and
nucleolus dissappears
Chromosomes
are replicated
Centrioles begin
to move to poles
Prophase
3:47
SPINDLE FIBERS
Prophase: The first phase of mitosis
1 chromosome – made up of 2 sister chromatids
Centromere
Sister chromatidsReplicated DNA
strands
Metaphase: The second stage of mitosis
• Chromosomes move to the equator of the
spindle – centromeres align
Centromere
Sister
chromatids
Metaphase
:30
Anaphase: The third phase of mitosis
• Spindle fibers pull centromeres apart
• Separates sister chromatids
• Begin to move to poles
Anaphase
:35
Telophase: The fourth phase of mitosis
• Chromosomes at the poles/centrioles
• 2 distinct daughter cells are forming
• Nuclei reforming; chromatin relaxing
• Cytokinesis beginning
• DIVIDES THE NUCLEAR CONTENTS! DNA!
Nuclear
envelope
reappears
Two daughter cells are formed
Telophase
1:15
Cytokinesis
• Divides cytoplasm and membrane of cells
• Differs between plants and animals– Animal cells “pinched” into 2 cells – “cleavage furrow”
– Plant cells divided by new cell wall = “cell plate”
• Cytokinesis- divides cytoplasm
• In animals, first sign
of cytokinesis (cleavage) is appearance of
cleavage furrow in
cell surface
Figure 12.5x Mitosis
Figure 12-09x Mitosis in an onion root
End Mitosis & Cytokinesis
Question 1
The stringy structures in the cell nucleus that
contain DNA are __________.
A. centromeres
B. chromosomes
C. genes
D. chlorophylls
Question 2
Look at the diagram and identify the stage of
mitosis that is depicted.
Centromere
Sister
chromatids
A. prophase
C. anaphase
B. metaphase
D. telophase
Question 3
What is the process by which a cell's cytoplasm
divides?
A. cytokinesis
B. telekinesis
C. meiosis
D. mitosis
Question 4
In multicellular organisms, groups of cells that
work together to perform a specific function are
called __________.
A. organ systems
B. organs
C. tissues
D. cell cycles
END
• Cytokinesis- divides
cytoplasm, typically follows
mitosis
• In animals, first sign
of cytokinesis
(cleavage) is
appearance of
cleavage furrow in
cell surface near
old metaphase plate
Figure 12.5x Mitosis
• Contraction of
protein fiber ring
pinches cell in
two
Cytokinesis in plants
• During telophase, vesicles
from Golgi fuse at
metaphase plate
forming cell plate.
–plate enlarges until
membranes fuse with
plasma membrane at
perimeter, with contents
of vesicles forming new
wall between cells
Figure 12.8 Cytokinesis in animal and plant cells
Figure 12-09x Mitosis in an onion root
Results of Mitosis
• When mitosis is complete, unicellular
organisms remain as single cells.
• In multicellular organisms, cell growth and
reproduction result in groups of cells that work
together as tissue to perform a specific
function.
Results of Mitosis
• Tissues organize in various combinations to
form organs that perform more complex roles
within the organism.
• Multiple organs that work together form an
organ system.
Results of Mitosis
Click image to view movie.
Mitosis