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http://alca.rutgers.edu/bio102/compwork.htm Biology Lecture Notes Dr. Transue Development A. History of Embryology     Spontaneous generation- it was figured out it wasn’t true in 1700. I. Pangenesis - “every organ contributes to the embryo.” Hippocrates 460-377 B.C.  : “humors” from organs (mixed together and the baby forms) II. Epigenesis- raw material; not every organ contributes to the embryo. Aristotle 384-322 B.C. : Vital heat “cooks” menstrual blood; he thought somehow the raw  materials in the blood form babies. III.    Epigenesis (1600’s): Everything comes from little “blobs”; simple building blocks IV. Preformation Either spermist or ovist “homunculus”- little person in sperm (spermist) or ovary (ovist);  this was proposed by Spallanzani. V. By Mid-1800 C.F. Wolff Epigenesis-  vis essentialis: gametes carry raw material. Microscopy-  affirms Harvey. VI. Pangenesis revisited: Darwin 1860, thought in gametes, each organ puts “gimmules”. VII. Modern Epigenesis: Mendel, Watson, and Crick -molecular genetics -cytoplasmic substances
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-control of gene expression Stages of Human Development Human development -echinoderms -frogs -chicken 1. Fertilization   I.  Anatomy of sperm and Egg. sperm : acrosome, vesicle inside sperm (acro=tip); carries enzyme to enable fusion of egg and  sperm. 48-07 pg 1064 egg : secondary oocyte (technically not egg) -corona radiata: follicle that gets ovulated -zona pellucida: non-cellular layer of material surrounding egg cell membrane. 48-18 pg  1075 Starfish Egg Anatomy:  -vitelline envelope (with jelly coat; it is analogous to the zona pellucida) II. Species Identification internal vs. external fertilization   very risky In Starfish: -binding on acrosome -receptors on vitelline (yolk) envelope In Mammals: -receptors on pellucida -    glycoprotein “ZP3” - cAMP signal transduction pathway initiated III. “Events” of Fertilization a. capacitation (after sperm is deposited) -in humans, in about 6 hrs. -molecules in female system (affect sperm)
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-HDL, progesterone b. acrosomal reaction begins (acrosomal membrane becomes easily broken if correct  species)  -acrosome releases hydrolytic enzymes (to break open egg membrane) c. Syngamy -at end of acrosomal reactions, cell membranes fuse. This occurs in the oviduct. -but Polyspermy! (introduction of several sperm into one ovum) 1. “Fast (Electrical) Block” -in place in 1-3 seconds -Ca ² influx (triggers depolarization of egg membrane so that no other sperm can infuse) - but repolarization takes place in about 1 minute 2. Slow Block: -takes over from fast block -permanent -internal Ca ² releases “cortical reaction”- cortical granules move to cell membrane and dump content between egg cell 
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