Download PowerPoint 113 Embryonic Development revised

Aim: How does an embryo
develop?
How does the zygote form?
Zygote – A fertilized egg
Embryonic Development:
Fertilization
Mitosis
+
Sperm
Egg
Zygote
Embryo- period of development from
zygote until about nine weeks.
What happens to the zygote
after it is formed?
Mitosis – causes the zygote
to repeatedly divide
producing the developing
embryo.
Cleavage
•Mitotic cell division
that occurs after
fertilization.
•During this time
period, the number
of cells increase
tremendously.
The result of cleavage is an embryo that is …..
Morula
A solid ball of cells which
moves towards the uterus
Mitosis continues & the embryo
becomes……
Blastocyst
A hollow ball of cells
Cell division continues & the
embryo starts to form a ….
Gastrula
• Folds inward
Gastrulation
• Three layers
• Each layer will
eventually form
the different
organ systems
CELLULAR DIFFERENTIATION
-cells undergo
cellular
differentiation,
in which the cells
become
increasingly
specialized in
structure &
function.
Gene Expression
Genes that are being
expressed are “on”
Though all genes are present in every
type of cell, only a small, specific section
of these genes are actually expressed or
turned on in each type of cell.
What makes some cells turn
“on” some genes while other
genes are “off”?
Environmental influences from within
the cell, from surrounding cells, or from
outside the organism.
Example: diet, toxins, sunlight, etc.
Differentiation’s ultimate goal
An embryo
with many
different types
of cells
Stem Cells
• Stem cells are
embryonic cells
that can turn
into any type of
cell in the body
How can stem cells help us?
• Can be used to
make any type
of cell that
needs to be
replaced in our
bodies
Why is the use of stem cells so
controversial?
• They are often
taken from
fetuses.
• Opponents
believe that you
are killing a life.
Are stem cells only
embryonic?
No, there are some
adult stem cells, but
they don’t have the
potential to become
any kind of cell
Why are they different?
These seeds
carry the same
genes for
chlorophyll:
CC
Grown in dark
Grown in light
ENVIRONMENT AFFECTS
GENE EXPRESSION