1. Embryonic Cell Development Studying embryonic development helps scientists understand the concept of cell differentiation during embryogenesis. Scientists use model organisms (organisms that represent developmental models of larger groups of organisms) to study the effects of different conditions and substances on the developing embryos. In embryonic development a single cell will undergo many divisions cell differentiation (process where the cells become specialized in structure and function) to become all of the different cell of the body. In order to accomplish this certain milestones must occur.

2. Cell differentiation occurs as genes turn on at the appropriate time and the appropriate place to signal the development of specialized structures. – genomic equivalence is demonstrated by taking a totipotent cell (cell capable of growing into an entire organism) and making a genetic clone of the organism from it plants - can demonstrate this by taking part of the root and growing an entire plant animals - can demonstrate by the process of nuclear transplantation where the nucleus of an unfertilized egg and replace it with the nucleus of a differentiated cell – demonstrated with Dolly the sheep – unfortunately Dolly developed complications of lung disease at age 6.Her DNA was as old as the inserted DNA. – cells become differentiated at specific times through the expression of tissue specific proteins evidence is in the appearance of mRNA associated with different cell types – cytoplasmic determinants from the mothers egg also signal differentiation in the developing cells change the cell through the process of induction Like structures must aggregate to form tissues via cell division.

3. Differences in plant and animal development Morphogenesis must occur as specific structures take form – occurs very early as ventral-dorsal, anterior-posterior, and lateral morphogenesis sets the stage for the developing organism Plant – morphogenesis and growth as not limited to juvenile period but occur throughout the life of the plant Animal – movement of cells and tissues is necessary for the development of 3 dimensional form

4. Why the interest in embryonic research? Stem cells! – can replicate itself indefinitely – can undergo differentiation to become different cell types embryonic stem cells are totipotent - can become ANY type of cells adult stem cells are pluripotent - can become many but not all types of cells