Gametogenesis makes sex cells by meiosis

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Lecture 13 Gametogenesis and
Fertilization
Gametogenesis makes sex cells by meiosis
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Gametogenesis gamete
formation by meiosis. Spermatogenesis
Sperm formation (1N) Oogenesis
Egg formation (1N)
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Spermatogenesis
Primary spermatocyte
2N
Meiosis
Secondary spermatocytes, 2N
1N
1N
1N
1N
1N
1N
Spermatids, 1N
morphogenesis
1N
1N
1N
1N
Sperm, 1N
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Spermatogenesis occurs in testes
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Cross section through testes tubes
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sperm
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flagella
Primary Spermatocyte Secondary
Spermatocyte Spermatid Sperm
2N
1N
1N
1N
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Sperm morphogenesis (change of shape)
Golgi complex
nucleus
mitochondrion
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Acrosome with digestive enzymes
Head
nucleus
Middle piece with mitochondria
tail
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Mitochondria
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Oogensis
Primary Oocyte
2N
Meiosis
Secondary oocyte
Polar Body
1N
1N
Polar body
Polar bodies
1N
1N
1N
1N
Ootid
morphogenesis
1N
Die
Ovum
Die
Die
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Secondary oocyte, 1N
Polar body, 1N
http//www.ucalgary.ca/UofC/eduweb/virtualembryo/P
ageMill_Images/image145.gif
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Ovary releases Secondary Oocyte and Follicle
Cells
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Release of secondary oocyte (1N) surrounded by
follicle cells (2N)
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Follicle Cells 2N nurse cells
Secondary oocyte 1N
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Plasma membrane
Sperm use acrosome enzymes to penetrate zona
pellucida
Egg (oocyte) cytoplasm
http//www.nature.com/ncb/journal/v3/n2/images/ncb
0201_e59_F1.gif
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Egg (oocyte) surrounded by follicle cells
Fertilization sperm egg
http//www.3ddoor.com/gallery/fertilization.jpg
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FERTILIZATION Two independent acts Egg
Activation Amphimixis (union of nuclei)
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Egg Activation when sperm contacts
egg membrane
http//www.luc.edu/depts/biology/dev/spersem.jpg
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Sperm on surface of the egg about to enter the egg
http//sun.science.wayne.edu/jram/zmfert.gif
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Amphimixis
when sperm and egg nuclei unit
http//www.southeasternfertility.com/graphics/vtou
rs_goodferteggs.jpg
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Aphids (small insects that suck nutrients from
plants). Females reproduce female offspring by
parthenogenesis until winter approaches then they
have sexual reproduction.
Parthenogenesis egg activation w/o amphimixis