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Animal Development I Where it all begins… 01-15.03.

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Presentation on theme: "Animal Development I Where it all begins… 01-15.03."— Presentation transcript:

1 Animal Development I Where it all begins…

2 Animal Development I  When does development begin? Where is the beginning of a circle!?*  Where should we start?  What is gametogenesis? Where do sperm come from? Where do eggs come from

3 Some Gamete questions…  Why are gametes required for sexual reproduction?  What makes gametes different from somatic cells? What is ploidy? Remember meiosis

4 Fig 12.5

5 Some Gamete questions…  How have gametes become specialized? Hint: think morphology…

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7 More about gametes  Where do sperm come from? Why do mammals have testes? What is the structure of testes? (fig 59.11, 13) What are germ cells? What are stem cells? How many sperm form from each germ stem cell?

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10 More about spermatogenesis  What is the progression from germ stem cell to sperm? What is a germinal cell (aka germ cell stem cell) What is a primary spermatocyte What is a secondary spermatocyte What are spermatids? What are spermatozoa? What do sertoli cells do?

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13 More about gametes…  What about eggs? What is their major cargo? Nutrients, cytoplasmic determinants, maternal chromosomes How do they protect themselves? What sort of structural adaptations do they display? What is a jelly coat? What is a vitelline membrane? What is a zona pelucida?

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15 More about eggs  How valuable are they? How many are made? When are they made available?  How do they find the sperm? Who finds whom? Are eggs motile?

16 More about eggs…  What are cytoplasmic determinants? mRNA, protein, other molecules Where are they located? When are they depositied? What is oogenesis? How are they distributed? What happens during cell division? What do they do? What is polarity?

17 Fig 17.14

18 More about eggs  Where do eggs come from? Why ovaries? What is the structure of ovaries? (fig 59.16)

19 More about eggs  Where do eggs come from? What cellular process is involved? Meiosis again… How many eggs form from each germ stem cell?

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21 More about eggs  How does egg structure differ between organisms? Jelly coat (sea urchin) vs. zona pellucida (mammal) No cell layer (sea urchin) vs. granulosa (mammal) Yolk differences More later…

22 Back to fertilization  What are model organisms?  What are the models for studying fertilization?  The rules of engagement…(fig 60.3) What does the sperm encounter first? How can it get through the jelly coat?

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24 More about fertilization  What is penetration (aka. the acrosome reaction)? (fig 60.3) Remember the acrosome? Remember the jelly coat/zona pellucida? What happens when the acrosome encounters jelly coat? What are the signals? What are hydrolytic enzymes? What do they do?

25 More about fertilization  More acrosomal reaction… How does the sperm penetrate jelly coat? What is the acrosomal process What happens at the vitelline membrane? Why are receptors important? What happens next? Sperm and egg membranes fuse HOORAY!!!

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27 More about fertilization  What is the situation? How many eggs are available? How many sperm are available? Only ONE winner!  What is polyspermy?  How is polyspermy prevented? Fast block to polyspermy Slow block to polyspermy

28 The fast block to polyspermy  What is membrane potential?  What happens to the membrane potential upon sperm fusion?  How does depolarization prevent polyspermy?  How long does the fast block to poplyspermy last?

29 The slow block to polyspermy  How does the slow block work? What is signal transduction? What are second messengers? Why do we need them?

30 More about the slow block  Where are intracellular Calcium stores? How is calcium release triggered? How does it radiate over surface of egg? Doing the Calcium wave…

31 Campbell fig 47.3

32 More about the slow block  What does calcium release do? Cortical granules fuse with PM Release contents into perivitelline space  What are cortical granules? Where are they located? What do they contain? enzymes mucopolysacchariddes

33 More about the slow block  What do mucopolysaccharides do in perivitelline space? Remember osmosis? How do mucopolysaccharides affect osmolarity? What does this do to perivitelline space?

34 More about the slow block  What do the enzymes from cortical granules do? What happens when polysaccharides become crosslinked? How would this affect sperm penetration?  How long does all of this take?

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36 What have we learned?  Preformation vs. Epigenesis  Fertilization Acrosome reaction Fast block to polyspermy Slow block to polyspermy (aka cortical reaction)

37 Next day  Cleavage and Morphogenesis


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