Embryo Development
Fertilization
During fertilization
several events occur:
• The nuclei of the egg
and sperm fuse.
• The zygote is
formed.
• Polyspermy is
blocked.
Cleavage
• Cellular division is mitotic not meiotic.
• Cleavage divisions form a small, solid ball of cells
called a morula.
Blastulation
• Cleavage continues until a hollow ball, the
blastula, is formed.
• The movement of the cells into an open interior
creates room for germ layers to develop.
Gastrulation
Germ Layers
Ectoderm
Endoderm
Ectoderm
Endoderm
Ectoderm
Endoderm
Archenteron
Blastopore
Organogenesis
Cell Differentiation
 Embyronic induction:
 “The action of one
group of cells on
another leads to the
establishment of the
developmental
pathway.”
Cell Differentiation
 Homeotic genes:
 “Genes that have
control over a whole
group of other genes
and the time at which
they are expressed.”
Cell Differentiation
 MicroRNA’s:
 The expression of various genes are regulated by
microRNAs.
RNAi Technology
Possible medical
applications:
Prevention of:
• Huntington’s disease
• HIV
• Hepatitis
• Measles
Protostomes vs
Deuterostomes
Protostomes vs
Deuterostomes
Protostomes vs
Deuterostomes
Determination of cell fate:
• The type of tissue or organ a cell will
become is determined:
• early in the developmental stage of a
protostome.
• late in the developmental stage of a
deuterostome.
Coelom Development
Embryonic Stem Cells
Embryonic stem cells are different from other cells by
their unique properties. They are:
• Totipotent
• Pluripotent
• Undifferentiated
• Uspecialized
Stem Cell Applications
Current medical applications of stem cell research:
• Repair of brain and spinal tissues.
• Treatment of diseases
• Cloning
• Reprogramming of diseased cells.
• Testing of new drugs.