Embryo Development

FertilizationDuring 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

EctodermEctoderm Ectoderm

Endoderm Endoderm 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 CellsEmbryonic 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.