Cell Reproduction
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Prokaryotes
Bacteria
Eukaryotes
Plants & animals
Prokaryotes
 Lack
a nucleus
 Have a single chromosome
 Reproduce asexually by binary
fission
 Include bacteria
Asexual Reproduction contd.

Binary fission
– happens in bacteria, amoeba, some algae
– one parent cell splits into 2 identical
daughter cells

Budding
– happens in yeast, hydra, corals
– parent produces a bud
– bud gets detached and develops into
offspring which is identical to parent
Steps in Binary Fission

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
Used by bacteria
Cells increase their
cell mass slightly
DNA & cell
components are
replicated
Each cell divides into
2 daughter cells
Binary Fission of Bacterial Cell
Budding
Eukaryotes
 Contain
a nucleus &
membrane bound organelles
 Asexually reproduce cells by
mitosis
 Also reproduce sexually
Sexual Reproduction in Animals

involves specialized sex cells called gametes
(haploid Cells)
 the union of a male and female gamete results in the
formation of a zygote that develops into a new
individual
Cell Cycle
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Stages in growth
& division
G0 Resting
Phase
G1 Phase
S Phase
G2 Phase
M Phase
Cytokinesis
G0 Phase
 After
Cell Division
 Cell At Rest
 From here some cells will
remain in the G0 Phase and
others will go into G1.
G1 Phase
 First
growth stage
 Cell increases in size
 Cell prepares to copy its
DNA
Synthesis Phase
 Copying
of all of DNA’s
instructions
 Chromosomes duplicated
G2 Phase
 Time
between DNA synthesis
& mitosis
 Cell continues growing
 Needed proteins produced
Mitosis Phase
 Cell
growth & protein
production stop
 Cell’s energy used to make 2
daughter cells (Diploid Cells)
 Called mitosis or
karyokinesis (nuclear
division)
Life Cycle of a Cell
Mitosis is a cycle with no beginning or end.
Interphase – Resting Stage
 Cells
carrying on normal
activities
 Chromosomes aren’t visible
 Cell metabolism is occurring
 Occurs before mitosis
Interphase
Stages of Mitosis
 Prophase
 Metaphase
 Anaphase
 Telophase
Cells Undergoing Mitosis
Steps in Prophase
 DNA coils
tightly & becomes visible
as chromosomes
 Nuclear membrane disappears
 Nucleolus disappears
 Centrioles migrate to poles
 Spindle begins to form
Prophase
Eukaryotic Chromosome
Human Chromosomes
Steps in Metaphase
 Spindle
fibers from centrioles
attach to each chromosome
 Cell preparing to separate its
chromosomes
 Cell aligns its chromosomes in
the middle of the cell
Metaphase
Steps in Anaphase
 Cell chromosomes are
separated
 Spindle fibers shorten so
chromosomes pulled to ends of
cell
Mitotic Spindle
Anaphase
Steps in Telophase
 Separation
of chromosomes
completed
 Cell Plate forms (plants)
 Cleavage furrow forms(animals)
 Nucleus & nucleolus reform
 Chromosomes uncoil
Telophase
Plant
Animal
Cytokinesis
 Occurs
after chromosomes
separate
 Forms two, identical
daughter cells
Cytokinesis
Cell Plate Forming in Plant Cells
Cell that do not go through
Mitosis
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Muscle Cell-Why? Fused fibers preventing cell
division
Some Neuron Cells –Why? Have lost there
centrioles and can no longer reproduce.
Blood Cells-Why? Mature and No longer have a
nucleus
Sex Cells: They go through meiosis.
Most of the cells never leave the G0 phase.
Cancer


Cancer is a disease of uncontrolled cell division. It starts
with a single cell that loses its control mechanisms due to
a genetic mutation. That cell starts dividing without limit,
and eventually kills the host.
Normal cells are controlled by several factors.
– Normal cells stay in the G1 stage of the cell cycle until
they are given a specific signal to enter the S phase, in
which the DNA replicates and the cell prepares for
division. Cancer cells enter the S phase without
waiting for a signal.
– Normal cells are mortal. This means that they can
divide about 50 times and then they lose the ability to
divide, and eventually die. This “clock” gets re-set
during the formation of the gametes. Cancer cells
escape this process of mortality: they are immortal and
can divide endlessly.
THE END