BIOL412 Chapter Notes - Chapter 20: Germ Layer, Gap Gene, Cell Potency
Document Summary
Outer layer of cells from membranes that surround the embryo developing in the inner cells: development of germ layers (ecto-, endo-, mesoderm) Pluripotency inner cells have the capacity to develop into any of the three germ layers. Multipotency cells within any one germ layer can develop into any cell type formed by that germ layer. The greater the cell specialization, the more unlikely it can be de-differentiated. Master genes at the top of the heap regulate expression or repression of the next lower gene set, etc. at a later stage of development. The higher the genes are in the pecking order, the more conservative (conserved) through evolution. Each successive group acts to refine and narrow the pattern of differentiation generated by previous groups. Example in fruit fly mutant larvae: 5 levels: level 1 bicoid" and nanos" mrna regulate hunchback" and caudal" proteins and 4 more levels mutants can be lethal. Homeotic (hox) genes specify identity of a body part (segment)
