The Cell Cycle and Cell Division
Chapter 3 Lesson 1 part 2
The Cell Cycle and Cell Division
How can one cell
become a multicellular
organism?
The Cell Cycle
There are two main phases in the cell
cycle—interphase and the mitotic phase.
Interphase
Interphase is the period during the cell cycle
of a cell’s growth and development Most of
the cells life is in interphase. During
interphase, most cells go through 3 stages:
• Rapid growth and replication, or
copying of the membrane-bound
structures called organelles.
• Copying of DNA, the genetic
information in a cell
• Preparation for cell division
Interphase – G1 phase
Cells increase in size
in Gap 1, produce
RNA and synthesize
protein. An important
cell cycle control
mechanism activated
during this period (G1
Checkpoint) ensures
that everything is
ready for DNA
synthesis.
Interphase – S phase
The complete
DNA instructions
in the cell must be
duplicated. DNA
replication occurs
during this S
(synthesis) phase.
Interphase – S phase
The cell’s DNA is
copied during the S
stage and is arranged
as pairs of identical
chromosomes called
sister chromatids.
This process is called
replication.
Interphase – G2 phase
During the gap between
DNA synthesis and
mitosis, the cell will
continue to grow and
produce new proteins.
At the end of this gap is
another control
checkpoint (G2
Checkpoint) to
determine if the cell can
now proceed to enter M
(mitosis) and divide.
Interphase – Mitosis or M phase
Mitosis or M Phase: Cell growth
and protein production stop at
this stage in the cell cycle. All of
the cell's energy is focused on
the complex and orderly
division into two similar
daughter cells. Mitosis is much
shorter than interphase, lasting
perhaps only one to two hours.
As in both G1 and G2, there is
a Checkpoint in the middle of
mitosis (Metaphase
Checkpoint) that ensures the
cell is ready to complete cell
division.
Mitosis
the equal distribution of the parent
cell’s genes between the 2 new
daughter cells.
Mitosis
During mitosis,
the contents of
the nucleus
divide, forming
two identical
nuclei.
Mitosis
Like interphase, mitosis is a
continuous process that scientists
divide into different phases:
• Prophase
• Metaphase
• Anaphase
• Telophase
Prophase
 first
phase of mitosis
 nuclear membrane disappears
 Copied chromatin coils
together condensing into
chromosomes
 the sister chromatids are
still attached by a
centromere
 nucleolus disappears
 spindle fibers form
Prophase
Prophase
Metaphase
 all
sister chromatids line
up single file at the
middle of the cell (the
center of the spindle)
 the period of time when
the centromere are on the
equatorial plane
Metaphase
Metaphase
Anaphase
 each
pair of sister
chromatids separates into 2
chromosomes called daughter
chromosomes(separated sister
chromatids)
 Spindle fibers begin to
shorten, pulling the daughter
chromosomes toward opposite
sides of the cell (poles)
Anaphase
Anaphase
Telophase
 it
begins when the daughter
chromosomes reach the end of
the spindle
 Nuclear membrane forms
around the chromatin
 daughter chromosomes begin
to uncoil
 nucleoli reappear
 Spindle fibers break down
 Two identical nuclei form
Telophase
Telophase
The 2 cells which result from
mitotic division followed by
cytokinesis are called daughter
cells.
Daughter cells are actually
cells entering interphase.
Daughter cells have exactly
the same genes as the mother
cell.
The purpose of mitotic cell
division is to insure that each
new daughter cell has genes
identical to those in the parent
cell.
The Mitotic Phase
The Mitotic Phase
The Mitotic Phase
The Mitotic Phase
Cytokinesis
In cytokinesis, the cytoplasm divides and
forms two new daughter cells.
cytokinesis
The division of the
parent cell’s cytoplasm
after mitosis is
finished.
Provides each daughter
cell with cytoplasm and
organelles.
Cell division varies in
different types of cells. Some
differences between plant and
animal cell division are:
• takes longer in an animal
cell than a plant cell
• plant cells don’t have
centrioles
• cytokinesis is different in
plant cells – forms a
division plate rather than
pinching in.
Results of Cell Division
The cell cycle is important for reproduction
in some organisms, growth in multicellular
organisms, replacement of worn out or
damaged cells, and repair of damaged tissues.
• In some unicellular organisms, cell
division is a form of reproduction.
• Cell division allows multicellular
organisms to grow and develop from
one cell.