BIOL 3454 1nd Edition Lecture 7 I II III IV V VI Chapter 8 Principles of development a Hans Spemann and Hidle Mangold i Tissue induction using salamander embryos ii Dorsal lip from salamander gastrula implant it on a host salamander then will get a new salamander Developmental biology a Single cell becomes a multicellular organism b Developmental biology fell behind fusion of genetics evolution functional molecular biology has closed the gap of understanding Historical ideas a Preformation the entire organism was in a miniaturized version w in a sperm or egg b Epigenesis origin upon or after an egg contains building material activated by sperm c Hierarchy of developmental decisions cellular and diversity arises sequentially d A cell which has committed to a fate it is determined by one of two processes i Specification ii Induction usually irreversible Oocyte maturation a Morphogenetic derminants transcription and inducing factors direct activation and repress genes at the correct times b At times fertilization occurs before the oocyte has undergone meiosis c Prophase I GVBD metaphase I metaphase II pronucleus Fertilization a Male female gametes unite to form zygote combo restores diploid chromosomal status b Timing of fertilization is highly veriable among organisms with regard to oocyte maturity c Sperm not always required for egg activation d Contact between egg and sperm i Species specific recognition proteins ii Prevent fertilization by another species iii Postmating prezygotic isolating mechanism iv Esp useful for gametes in water e Contact and prevention of polyspermy i n n 2n n n n Xn not good f Fast block electrical potential charge change in the egg membrane g Slow block cortical rxn thousands of enzyme capsules release their contents between the egg membrane and vitellene envelope h Creates an osmotic water rushes in sperm washed away Later causes the vitellene membrane to harden and physically block sperm Sea urchin fertilization a Easy to find cheap These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute VII VIII IX X XI XII XIII b Fertilization external easy in lab c Embryo transparent easy to see development d Very historic Aristotle Cleavage and early development a Blastomeres small maneuverable cells b No growth just a big mass dividing to a group of normally sized cells c Polarity established animal pole vegetal pole Yolk distribution a Isolecithal very little yolk evenly distributed b Mesolicithal moderate amount of yolk at vegetal pole c Telolecithal lots of yolk at vegetal pole d Centrolecithal large centrally located yolk Cleavage a Meroblastic lots of yolks cells sitting on top of undivided yolk b Holoblastic cleavage furrows extend completely though the egg Direct vs indirect development a Direct development embryo to a miniature adult b Indirect development multiple developmental stages c Either can be shortcut by matrotrophy where the mother nourishes the developing embryo Development following cleavage a Blastula cluster of cells usually hollow space is the blastocoel one layer of germ cells one tissue layer Gastrulation the formation of two germ layers a Gastrulation the conversion of the spherical blastula into a two or three layered embryo b Archenteron the internal pouch formed in gastrulation c Blastopore the opening to the archenteron Developmental layers a Three primary germ cell layers triploblastic i Ectoderm most exterior becomes integument nervous system ii Endoderm most of the GI tract most of the internal organs iii Mesoderm most connective tissues fluids and muscles