Download Embryo - Manhasset Schools

How does an embryo develop?
How does the zygote form?
Zygote – A fertilized egg
What happens to the zygote
after it is formed?
Mitosis – causes the zygote to
repeatedly divide producing the
developing embryo.
Embryonic Development:
Fertilization
Mitosis
+
Sperm
Egg
Zygote
Embryo- the stage in human development from the
first division of the zygote until about nine weeks
after fertilization.
Cleavage
•The term used to
describe the early cell
division associated with
embryonic development.
•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 ….
Gastrula • Fold inwardly
Gastrulation
• Three layers
• Each layer will
eventually form the
different organ
systems
CELLULAR DIFFERENTIATION
• Due to gene
expression, 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 of the genome are present in every
type of cell, only a small, specific fraction of these
genes are actually expressed 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.
Why are they different?
These seeds
carry the same
genes for
chlorophyll:
CC
Grown in dark
Grown in light
ENVIRONMENT AFFECTS
GENE EXPRESSION
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
A Cell Stem Story
Award-winning 15 minute video introduction to stem cell
research
http://www.eurostemcell.org/films