Transcript Lesson 6 ( Cellular Reproduction)

Whiteboard Protocol
•Bell Work: What is the product on the photosynthesis
reaction?
•Objective: TLW how to write the steps of the mitosis.
•Classwork:
http://www.oxnardsd.org/Portals/36/Users/220/20/220/mitosis_work
sheet.pdf
•Homework: Biology book, page 260-263; Question 140
•Exit Slip: Name to step in mitosis
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Cell Reproduction
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Prokaryotes
Bacteria
Eukaryotes
Plants & animals
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Prokaryotes
 Lack
a nucleus
 Have a single chromosome
 Reproduce asexually by binary
fission
 Include bacteria
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Asexual Reproduction contd.
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Binary fission
– happens in bacteria, amoeba, some algae
– one parent cell splits into 2 identical
daughter cells
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Budding
– happens in yeast, hydra, corals
– parent produces a bud
– bud gets detached and develops into
offspring which is identical to parent
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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
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Binary Fission of Bacterial Cell
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Budding
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Eukaryotes
 Contain
a nucleus &
membrane bound organelles
 Asexually reproduce cells by
mitosis
 Also reproduce sexually
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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
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Cell Cycle
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Stages in growth &
division
G0 Resting Phase
G1 Phase
S Phase
G2 Phase
M Phase
Cytokinesis
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G0 Phase
 After
Cell Division
 Cell At Rest
 From here some cells will
remain in the G0 Phase and
others will go into G1.
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G1 Phase
 First
growth stage
 Cell increases in size
 Cell prepares to copy its
DNA
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Synthesis Phase
 Copying
of all of DNA’s
instructions
 Chromosomes duplicated
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G2 Phase
 Time
between DNA synthesis
& mitosis
 Cell continues growing
 Needed proteins produced
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Mitosis Phase
 Cell
growth & protein
production stop
 Cell’s energy used to make 2
daughter cells (Diploid Cells)
 Called mitosis or
karyokinesis (nuclear
division)
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Life Cycle of a Cell
Mitosis is a cycle with no beginning or end.
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Interphase – Resting Stage
 Cells
carrying on normal
activities
 Chromosomes aren’t visible
 Cell metabolism is occurring
 Occurs before mitosis
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Interphase
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Stages of Mitosis
 Prophase
 Metaphase
 Anaphase
 Telophase
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Cells Undergoing Mitosis
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Steps in Prophase
 DNA coils
tightly & becomes visible
as chromosomes
 Nuclear membrane disappears
 Nucleolus disappears
 Centrioles migrate to poles
 Spindle begins to form
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Prophase
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Eukaryotic Chromosome
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Human Chromosomes
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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
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Metaphase
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Steps in Anaphase
 Cell chromosomes are
separated
 Spindle fibers shorten so
chromosomes pulled to ends of
cell
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Mitotic Spindle
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Anaphase
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Steps in Telophase
 Separation
of chromosomes
completed
 Cell Plate forms (plants)
 Cleavage furrow forms(animals)
 Nucleus & nucleolus reform
 Chromosomes uncoil
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Telophase
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Plant
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Animal
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Cytokinesis
 Occurs
after chromosomes
separate
 Forms two, identical
daughter cells
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Cytokinesis
Cell Plate Forming in Plant Cells
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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.
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Cancer
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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.
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THE END
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