It is also possible to have identical quadruplets from the four cell stage, but after more cell divisions, the cells no longer can form a complete human. Cell differentiation is a process whereby only some cells become activated to produce particular proteins. The genes for other proteins are not lost , but are inactive. An experiment showed that an enucleated egg, fertilized with the nucleus from an intestine cell could produce a whole frog. Morphogenesis Morphogenesis is the shaping of the embryo toward its final form.
Cells divide, grow and migrate.
The cells are responding to chemical concentration gradients, surface proteins on other cells, and other cues from surrounding cells. Cells can move like amoebae and crawl between other cells to reach their destination. Differential growth can form folding sheets of cells that finally take on the shape and conformation of organs. Cellular proteins can elongate, link together et. and change the shape and other characteristics of cells of cells as the cells that form the cornea. There is also programmed cell death as in the absorption of a tadpole tail.