Brittany
Amanda
Biology
9/23/03
 G1 phase
 S phase
 G2 Phase
 Mitosis
 Prophase
 Metaphase
 Anaphase
In this presentation, all of the phases  Telophase
of the cell cycle will be covered. We
 Cytokinesis
will start with the G1 phase and
continue until the last phase of the
 Meiosis
cycle. The order is as follows:
• Sometimes called Interphase.
• The formation of two daughter cells from a parent cell in
cytonkinesis is an energy-consuming process. The time
needed by the new cells to replenish their energy
causes this “gap”.
• After cell energy reserves are restored, the daughter
cells begin to grow.
• This is the longest phase of the cell cycle.
• Synthesis means to make.
• After a period of growth, each cell's original DNA
is duplicated in the process of replication or the
process of duplicating the DNA molecule.
This is a
chromosome that
is found in the cell
during cell division.
S PHASE IS ALSO KNOWN AS THE
SYNTHESIS PHASE OR DNA SYNTHESIS.
• During the G2 Phase, the cell again
undergoes growth and protein synthesis
because it needs enough proteins for the 2
cells it will split into, priming it to be able to
divide. Once this is complete, and has gone
through many checkpoints along the way, the
cell finally enters the fourth and final phase of
the cell cycle. This phase is known as the M
(Mitosis) phase.
• The replication of DNA is another energy-consuming process
for the cell. The time taken by a cell to build up its energy
reserves produces this second "gap".
• Mitosis is the process by which DNA is divided into
two identical daughter sets before the cell divides.
• There are four stages that occur before the cell is
completely split apart. They are:
Prophase
Anaphase
Metaphase
Telophase
• Early prophase: chromatin coils to form chromesomes,
nuclear membrane disappears, and centrioles migrate to
opposite poles of the cell.
• Middle prophase: spindle fibers, microtubules of protein,
begin developing.
• Polar fibers extend across the cell from
centriole to centriole.
• Kinetiochore fibers extend from the
centromeres of a chromosome to the centrioles.
• Late prophase: protein fibers called asters
radiate from each centriole in animal cells.
• In this phase, kinetochore fibers move the chromosomes
to the equator of the cell.
Movement
taking place
during
metaphase.
• Each chromosome has reached its maximum density.
• The homologous pairs and their sister chromatids interact
with fibers which form from either side of the nuclear
envelope of the cell. These fibers are procudes from the
centriole. There is a centriole at the opposite ends of the cell.
• The chromosomes are then lined by the fibers at what is
known as the metacentric plate, which is located in the
center.
The separation of the
fibers to opposite poles.
• Pulls apart the tetrad,
separating each
homologous chromosome.
• The centromere of each
pair of chromatids divides,
the chromatids separate
and are pushed to opposite
poles of the cell by the
combined efforts of the
fibers, all in one quick
motion.
• All fibers disappear.
• Chromatids unwind and stretch to form
chromatin.
• A nuclear membrane forms around each
mass of chromatin, splitting the cytoplasm
into two separate parts.
• Then interkinesis will follow, which is a
resting period.
Membranes forming,
showing the division
of the cytoplasm.
Detailed events
occurring in cytokinesis.
• The division of the cytoplasm of a parent cell.
(the cell pinches together in the center)
• While each daughter cell gets identical sets of
DNA, the cytoplasm and organelles are only
roughly divided equally between the two cells.
THE
FINAL
STAGE
OF
MITOSIS
Meiosis I • DNA replication takes place.
• A parent cell produces two daughter
cells with one member of each original
pair of homologous chromosomes.
Meiosis II • There is no DNA replication.
• The chromatids of each chromosome
separate and each daughter cell divides.
• At the end of Meiosis, there are four
daughter cells from each parent cell. Each
daughter cell has half the number of
chromosomes of the parent.
The process of Meiosis is more
complicated than the single division of
Mitosis because it provides more
opportunity for genetic variation.
Covered in this presentation was the cell cycle in detail. It
was learned that the steps within this cycle are:
• G1 phase - energy consuming process.
• S phase - DNA duplication.
• G2 Phase - growth and energy synthesis.
• Mitosis - equal division of DNA.
• Prophase - 2 centrosome move to opposite poles.
• Metaphase - chromosomes move to equator of cell.
• Anaphase - fibers separate to opposite poles.
• Telophase - nuclear membrane forms around the 2 cells.
• Cytokinesis - division of the cytoplasm and organelles.
• Meiosis - two divisions in sequence.
Cells and the Cell Cycle - Day 3. 2003. Desert Vista High School. 24
September 2003.
<http://staff.tuhsd.k12.az.us/gfoster/standard/bcell2.htm>
Cell Cycle Regulation. 2003. University of Pennsylvania
<http://www.geocities.com/CollegePark/Lab/1580/cycle.html>
Metaphase I. 1997. North Carolina State University
<http://www4.ncsu.edu/unity/users/b/bnchorle/www/metai.htm>
Anaphase I. 1997. North Carolina State University
<http://www4.ncsu.edu/unity/users/b/bnchorle/www/anai.htm>
Telophase I. 1997. North Carolina State University
<http://www4.ncsu.edu/unity/users/b/bnchorle/www/teloi.htm>
CYTOKINESIS. 1999. The University of Manchester <http://www.teachingbiomed.man.ac.uk/ramsay/Cytok.htm>
Meiosis. 1999. National Health Museum
<http://www.accessexcellence.org/AB/GG/meiosis.html>