Transcript cell cycle - Fort Bend ISD

Cell Growth
Does an animal get larger because each cell
increases in size or because it produces more
of them?
Mature red blood cells are not capable of dividing, as they do not possess nuclei.
Therefore, it is not possible that red blood cells will divide as they travel along our
blood vessels. New red blood cells are produced in the red bone marrow of long
bones in adults, not from the cell division of mature red blood cells.
"RBCs are terminally differentiated; that is, they can never divide. They live about
120 days and then are ingested by phagocytic cells in the liver and spleen."
Cell Growth
As you might have guessed, living things grow
by producing more cells.
 The koalas have the same size cells, just one
has more then the other.
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Why DO Cell’s Divide ..
#1
reason is because as volume
increases:
More demand is placed on cell’s DNA
(DNA Overload)
More difficult to bring in enough
nutrients and get rid of waste (material
exchange)
#2 Ratio of surface area to volume.
•Before cell division the cell replicates
all of its DNA.
Chromosomes
In eukaryotic cells, the genetic
information that is passed on from
one generation of cells to the next
is carried by chromosomes.
 The cells of every organism have
a specific number of
chromosomes.
 Each chromosome consists of two
identical “sister” chromatids.
When the cell divides, the “sister”
chromatids separate and go to
each of the new cells.
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Chromosome
Each pair of chromatids is attached at an area
called a centromere.
 Centromeres are usually located near the
middle of the chromatids, although sometimes
can be found at each end.
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CELL CYCLE
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Mitosis is a process where cells are produced
for growth and/or replacing damaged or old
cells
The process by which a cell reproduces to
create two identical copies is known as
mitosis.
Cells formed by mitosis are known as
daughter cells.
The cell division process occurs in several
different stages, known collectively as the
'cell cycle'.
Many of the abnormal traits of cancer cells
are due to defects in genes that control cell
division.
Cell Cycle (phases)
Interphase-
cell
resting (G1, S, G2)
M Phase- Cell
actively dividing
(this occurs during
Mitosis (M) or
Cytokinesis, C)
Cell Cycle
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The cell cycle consists of four stages  G1, S,
G2, and M and then cytokenesis.
G1 and G2 are 'gap' phases.
G1 phase (primary growth phase) –cell gets bigger
S in the synthesis phase in which the chromatin
(DNA) is copied (replicated).
G2 (gap 2) –cell prepares to divide, organelles
replicate
M is the mitotic phase in which the cell physically
divides into two daughter cells. Has 4 subphases!
Most cells are NOT actively dividing. These cells
Mitosis (M phase) steps which include the
process for asexual cell division.
 Biologists divide the events of mitosis into
four phases:
- Prophase
- Metaphase
- Anaphase
- Telophase
Depending on the type of cell, the four
phases may last anywhere from a few
minutes to several days.
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The kinetochore is the
protein structure on
chromosomes where the
spindle fibers attach during
cell division to pull the
chromosomes apart.
The kinetochore forms in
eukaryotes, assembles on
the centromere and links
the chromosome to
microtubule polymers from
the mitotic spindle during
mitosis and meiosis.
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PROPHASE
The first and the longest phase of mitosis, prophase
can take as much as 50 to 60 percent of the total time
required to complete mitosis.
Chromosomes condense, the nuclear membrane breaks
down, and spindle fibers form , centrioles move to
opposite ends.
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METAPHASE
The replicated
chromosomes line up in
the middle of the cell
Chromosomes attach to
spindle fibers
ANAPHASE
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Chromosomes separate at the centromere and the cell
becomes elongated, with distinct ends (poles).
TELOPHASE
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Chromosomes gather
at opposite ends and
start to unwind
Spindles break down
Nuclear envelopes reform at the two poles
and new cell
membranes begin to
form to create two
independent cells
CYTOKINESIS
the division of the cytoplasm to make two complete daughter cells
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ANIMAL CELLS
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Cell membrane pinches apart
into two equal parts with one
nucleus in each daughter cell
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PLANT CELLS
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Cell plate forms between two
nuclei
Cell plate develops into a cell
wall
Animations
http://www.youtube.com/watch?feature=player_detailpage&v=VlN7K19QB0
http://www.johnkyrk.com/mitosis.html
http://www.hybridmedicalanimation.com/anim_mitos
is.html
Activity
Pass out white boards to students (groups
of 2-3)
 Flip through the following slides and have
students either draw or label the picture
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CYTOKINESIS
METAPHASE
PROPHASE
ANAPHASE
Cell Cycle Regulators
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Scientists discovered
that cells in mitosis
contain a protein called
cyclin when injected in
a non-dividing cell,
would cause a miotic
spindle to form.
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Cyclins regulate the
timing of the cell cycle
in eukaryotic cells.
Uncontrolled Cell Growth
Why is cell growth regulated so carefully?
 Cancer- a disorder in which some of the
body’s own cells lose the ability to control
division. Cancer cells do not respond to the
signals that regulate the division of most cells.
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