Chapter 47 Animal Development

Fertilization Egg sends out chemical signals for sperm to find it Sperm capacitation refers to the physiological changes spermatozoa must undergo in order to have the ability to penetrate and fertilize an egg. Hyaluronic acid – on sperm, eats away the cumulus cells Cumulus cells – were follicle cells earlier Zona pellucida – membrane under cumulus cells, has proteins: ZPI – don’t need to know, it’s a linker ZPII – second protein; encourages the egg to take in the sperm ZPIII – first protein; sperm binds and acrosome comes out and eats through zona

Preventing Polyspermy Cortical granules act as IP3 system (release calcium) when sperm makes it in Cuts off ZPIII Changes the composition of the zona (so another acrosome can not penetrate because its enzymes wouldn’t work)

Specializing the cells After Fertilization Cell division 1 Differentiation Specializing the cells 2 Morphogenesis Forming the embryo 3

Cleavage Grey crescent – lots of magical substances/ information

Experiment Read more: http://www.biology-pages.info/S/Spemann.html

Nervous system development Notochord tells ectoderm to become nervous system First organ system to develop Neural plate forms neural tube Defects Spina Bifida Anencephaly

Malformations/Birth Defects Most body systems are developed during the first three months of pregnancy, so birth defects can develop very early Thalidomide Drug in the 1950s and 1960s Inhibited long bone formation, so babies were born with very short arms/legs X-rays Could kill primordial germ cells Fetal Alcohol Syndrome