Mitosis and the Cell Cycle
Mrs. Schenfield’s
th
8 Grade Life Science
The Importance of Mitosis
Growth and Repair
 Reproduction of single celled
organisms.

The need to heal!
The need to grow!
Cell Cycle
 95%
of cell cycle in interphase
 5% of cell cycle in mitosis
ending with cytokinesis.
Cell Cycle-Interphase (G1, S, G2)



G1 = cell grows
S = genes (DNA)
duplicated
G2= Prepares to divide
M= Mitosis-cell
goes through prophase,
metaphase, anaphase,
and telophase.

“G1” or Growth
1 phase (Interphase)
“S” or DNA
Synthesis
(Genes copied)
INTERPHASE
G2 or Growth 2
phase-Prepares
to become two
cells.
“M” or
Mitosis
phase
How are genes
duplicated?
DNA Replication –
Simple in Principle,
Complicated in Practice

During the “S”
period of
interphase the
DNA uncoils and
an exact copy is
made of each
side.
D
DNA is packaged into
chromosomes.
The Link Between DNA Replication and Chromosome Duplication
Chromosomes


Chromosomeconsists of two
identical halves
connected together
by a centromere.
Chromatid- a half of
one chromosome.


Contains one
complete set of
information
Copies itself to
make the other
chromatid
DNA is Condensed into Visible Chromosomes Only
For Brief Periods in the Life of a Cell
95% of the time,
chromosomes are like
this.
Chromosomes can be seen 5%
of the time in an actively
growing cell and less in a nongrowing cell.
Cell division requires coordinated division of
chromosomes (mitosis) …..
…… and division of the
cytoplasm (cytokinesis).
Stages of Mitosis





Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Cancer Is One Outcome of A Runaway Cell Cycle
Picture of prostate cancer cells during division.
The Knit of
- Mitosis
Precisely andin
Evenly
Dividesof
Dividing
theIdentity
duplicated
chromosomes
the phases
Duplicated Chromosomes
mitosis provides each new cell with an identical and
complete set of genes.
The sister
chromatids line
up at the center of
the spindle.
interphase
Prophase
Metaphase
Mitosis Precisely and Evenly Divides Duplicated Chromosomes
Cytokinesis is the process of cell division and
it is distinct and separable from mitosis.
.
Mitosis in Action
Blue shows DNA,
green shows spindle
fibers.
Interphase
Early prophase
Late prophase
Early metaphase
Metaphase
Early anaphase
Late anaphase
Late telophase
In Animal Cells,
a Cleavage
Furrow Forms
and Separates
Daughter Cells
(Cytokinesis)
Actual picture of a cell using
an electron microscope.
Cleave furrow in a dividing frog cell.
The Plant Cell Wall Forces Cytokinesis to
Play by Different Rules
Use your notes to identify the stage
of mitosis each cell is in.
Cell #1
Cell #2
Stage?
Cell #3
Cell #4
Stages?
Cell #5
Cell #6
Stages?
Cell #7
Cell #8