CELLULAR REPRODUCTION
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Students know and understand the
characteristics and structure of living things,
the processes of life, and how living things
interact with each other and their environment.
Benchmark 3.10: Cell reproduction/division
has various processes and purposes (mitosis,
meiosis, binary fission)
Assessment objective 3.10a: Compare and
contrast the purposes and processes of mitosis,
meiosis, and binary fission.
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It was once thought that some nonliving things could
give rise spontaneously to living things.
Aristotle (384-322) and others believed that living
organisms could develop from non-living materials.
1688: Francesco Redi (1626-1678) was an Italian
physician who refuted the idea of spontaneous
generation by showing that rotting meat carefully kept
from flies will not spontaneously produce maggots.
1861: Louis Pasteur's (1822-1895) famous experiments
with swan-necked flasks finally proved that
microorganisms do not arise by spontaneous
generation.
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Cell reproduction occurs when parent cells
divide.
Cells divide rather than grow really big
because as the volume of cytoplasm increases,
the surface area of the plasma membrane can’t
keep up and eventually the cell would either
starve from lack of nutrients or poison itself
because of excess wastes.
Cells stop growing or reproduce before either
of those things happens.
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A cell’s activity is regulated by DNA
which is organized into hereditary
units called genes.
The genes code for RNA and protein.
DNA is organized and packaged into
structures called chromosomes.
Prokaryotic cells have a single
circular molecule of DNA. What is a
prokaryotic cell?
Eukaryotic cells have many more
genes. A human cell contains 46
separate, linear DNA molecules that
are packaged into 46 chromosomes.
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DNA and proteins make up a
substance called chromatin.
The first level of DNA
packaging is done by 8 histones
(proteins) that come together to
form a histone core.
The structure made up of a
histone core and the DNA
around it is called a nucleosome.
Chromosomes exist as coiled or
uncoiled nucleosomes. As the
cell prepares to divide, the
chromosomes condense even
further so that the DNA
molecules don’t get tangled up.
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Chromosomes are made up of
two thick strands, called a
chromatid, made up of a single
DNA molecule.
Identical pairs, called sister
chromatid are held together in
the middle by a centromere.
During cell division, the sisters
are separated at the centromere,
then each ends up in a daughter
cell, that way each cell has the
same genetic material.
DNA SONG!!!!
Chromatin, chromosomes and DNA subunits. 3:45
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Three types of cell
division
Prokaryotic is binary
fission—the DNA
molecule is attached to the
inner cell membrane. It
builds a cell membrane
between the two copies of
DNA while a new cell
wall forms around the
membrane, squeezing the
cell and pinching off two
daughter cells.
Mitosis and Meiosis are
eukaryotic and more
complex.
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Interphase and Mitosis
make up the cell cycle.
Interphase is the nonreproducing phase of cell
life.
Mitosis is the
reproductive phase of a
cell’s life.
Most of the cell’s life is
spent in interphase.
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Interphase is the cell’s
non-reproducing stage.
Cells spend most of
their life in this phase.
During interphase, each
chromosome and the
DNA it contains makes
exact copies.
Mitosis follows
interphase.
Cell song (mitosis)
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The chromatin in the
nucleus starts forming
loops and condensing,
growing shorter and
thicker.
In animal cells, the two
pairs of centrioles begin to
separate and migrate to
opposite poles of the cell.
Microtubules form
between the two pairs of
centrioles and form a
football-shaped structure
called a spindle.
All eukaryotic cells have
spindles.
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The nuclear membrane
disappears.
Chromosomes are
double-stranded
structures which shows
that replication has
occurred.
Each strand is a replica
of the other and called a
chromatid.
Two chromatids of a
chromosome are called
sister chromatids and
are joined in the middle
by a centromere.
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Chromosomes are
scattered randomly in
the area where the
nucleus was.
They then move
toward the spindle’s
equator when the
microtubules attached
to each centromere
change in length.
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The centromeres split
and the two sister
chromatids of each
chromosome begin to
separate from one
another and move
apart.
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The overlapping
microtubules from each
pole join and begin to
lengthen as proteins are
added.
The poles are pushed
apart, and sister
chromatids are pulled
to opposite poles of the
cell.
Each end of the cell has
one set of singlestranded chromosomes.
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In animals, two cells are
formed from the one as the
cell begins to pinch together
at the center and the
microfilaments attached to
the membrane contracts.
In cell walls (plants), a cell
plate grows outward from
the middle of the cell.
A nuclear envelope forms
around the chromosomes at
each pole of the cell. The
chromosomes uncoil and
change back to their original
chromatin form.
The spindle dissolves and
mitosis is complete.
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Daughter cells
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Cytokinesis follows the end
of mitosis. After telophase,
the process reverses and
nucleoli reappear. The 2
nuclear membranes enclose
each set of chromosomes.
The chromosomes become a
mass of chromatin.
The cytoplasm is separated
and two cells called daughter
cells are formed.
Each daughter cell is about
half the size of the original
cell and have the same
genetic material.
Both then enter the G1 stage
of interphase.
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Cell division is highly controlled by signals
from proteins and other environmental signals.
Proteins control the phases of the cell cycle.
Proteins and other organs control cell growth
and division.
Environmental conditions such as nutrient
availability affect the cell cycle.
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G1: Cell checks surroundings to determine if
conditions are favorable and the cell is healthy and
large enough. If so, it enters the synthesis phase.
G2: Before mitosis, cell checks for any mistakes in
the copied DNA. Enzymes correct mistakes.
Proteins also check to see if the cell is large
enough. Once everything checks out, the cell
undergoes mitosis.
Mitosis: During metaphase, cell checks to make
sure chromosomes are properly attached to
spindle fibers to ensure equal distribution of
genetic material to the daughter cells.
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Cancer is a group of severe and sometimes fatal
diseases caused by uncontrolled cell growth.
Uncontrolled cell growth and division can result in
masses of cells that invade and destroy healthy
tissues.
DNA can cause the cell to respond improperly or
to stop responding. If the cell cycle is not
controlled, the defective cell divides to produce
more defective cells that can eventually form a
mass called a tumor.
Mitosis in cancer: 0:28
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Benign tumors do not spread to other parts of
the body and can often be removed by surgery.
A malignant tumor can spread through the
body in a process called metastasis (1:00) .
Some cancers are treated with drugs in a
procedure called chemotherapy as well as
surgery or radiation therapy.
The best way to prevent cancer is to avoid
things that can cause it such as ultraviolet light
or chemicals found in products such as
cigarettes.