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Development

Development. Rachel Miller. Gamete Formation. Eggs develop in female’s ovaries - female is born germ cells in ovaries begin meiosis - division stops at prophase I - ovarian cells become primary oocytes - finish meiosis with fertilization by sperm. Gamete Formation.

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Development

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  1. Development Rachel Miller

  2. Gamete Formation • Eggs develop in female’s ovaries - female is born germ cells in ovaries begin meiosis - division stops at prophase I - ovarian cells become primary oocytes - finish meiosis with fertilization by sperm

  3. Gamete Formation • Sperm develop in male testes - begins at puberty - spermatogenesis takes 64 days - several million sperm produced per day

  4. Incorrect Gametogenesis can Cause: • Down’s Syndrome • Klinefelter’s Syndrome • Edwards Syndrome • Spontaneous abortion

  5. Embryonic Development • Fertilization • Cleavage • Morula • Blastula • Gastrula • Extraembryonic Membrane Development

  6. Fertilization • Recognition - sperm secretes protein - binds with special receptor molecule on the zonapellucida - zonapellucida- glycoprotein membrane surrounding oocyte - insures fertilization between same species

  7. Fertilization 2) Penetration - sperm and oocyte plasma membranes fuse

  8. Fertilization 3) Fertilization membrane forms to block any more sperm

  9. Fertilization 4) Oocyte undergoes meiosis II - produces an ovum and polar body - polar body released

  10. Fertilization 5) Sperm and ovum nuclei fuse - zygote nucleus of 23 chromosomes

  11. Cleavage • Rapid cell divisions without cell growth • Microfilaments contract and pinch cell in two • Form smaller blastomeres

  12. Cleavage • Cytoplasmic Localization • Blastomeres receive different maternal messages • Inherit different proteins • Determines later cell lineages

  13. Cleavage

  14. Mammal Cleavage • Embryos genome produces proteins for cleavage to occur • Mammals take 12-24 hours for each cut • Mouse and goat- maternal to zygotic control at two cell stage • Have rotational cleavage

  15. Day 4: Morula • Ball of 16- 32 cells

  16. Blastula • Liquid fills morula and pushes cells out • Hollow, single layer of cells

  17. Day 5: Blastocyst • Inner cell mass- few cells that will become actual embryo • Zonapellucida • Trophoblast- develop into placenta • Blastocoel- fluid filled cavity

  18. Days 6-7: Blastula Hatches • Blastocyst adheres to uterine lining • Injected out of ZonaPellucida • Has now formed connections with mother’s tissues

  19. Ectopic Pregnancy • Fertilized egg implants outside of uterus • Typically occurs in fallopian tubes • Fetus will burst organ

  20. Days 10-14: - Fluid filled amniotic cavity opens up - Amnion forms- will enclose embryo - buoyant cradle and nourishment -Yolk sac starts to form- will make blood and germ cells - Embryo starts to form from embryonic disc - Chorion (placenta) starts to form

  21. Days 10-14 1. Start of the embryonic disc 2. Amniotic cavity- filled with fluid -buoyant cradle and nourishment 3. Yolk sac- gives rise to blood and germ cells 4. Chorion (placenta) starts to form 4

  22. Day 15: Gastrula • Single layered blastula becomes double layered • Opening to outside

  23. Day 15: Gastrula • 3 Germ Layers for tissue to develop from - Ectoderm, Mesoderm, Endoderm • Archenteron- center cavity • Blastopore- opening

  24. Days 18-23: Morphogenesis • Organs begin to form • Tissues fold • Neural folds merge to make start of spinal cord and brain • Somites- will become bones and dermis

  25. Day 24-25 Pharyngeal arches will become: - face - neck - mouth - nasal cavities - larynx - pharynx

  26. Differentiation • All cells started out with same genes (from one fertilized egg) • All transcribe many of same genes • Most have special functions - Ex. red blood cells transcribe genes for hemoglobin • Over time specific subsets of genes have been turned on

  27. Inductive Cell from One Group Influences Development of Another

  28. Pattern Formation • Sculpting of specialized tissues and organs from clumps of cells in proper places in embryo in proper order • Embryonic cell reads it genes • Makes and secretes molecules to neighbors • These signals induce changes

  29. Cadherin and Integrin Signals • Proteins that affect how cells link up in gastrula - will affect how organs form • Signals activate/ inhibit adhesion proteins

  30. HOX Genes • Class of master genes that contain information about mapping out of body plan

  31. HOX Genes • All body appendages start out as tissue buds • Bud forms where Dll gene is expressed - turned on- arm/leg forms - turned off- nothing • Hox genes suppress DII when needed • DII expressed similarly across phyla

  32. Fate Mapping • shows how a cell or tissue moves and what it develops into

  33. Polymelia • Results in extra limb(s) - usually shrunken/deformed

  34. Conjoined Twins • normal identical twins- the egg splits at four to eight days after fertilization • conjoined twins- the split occurs sometime after day 13 • Embryos do not fully separate

  35. Rare Types • Dicephalus: Twins that share one body, but have two separate heads and necks. • Parasitic twins: This occurs when one smaller, malformed twin is dependent on the larger, stronger twin for survival. • Fetus in fetu: In this unusual case, one fetus grows inside the body of the other twin "Conjoined Twins Information on Healthline." Medical Information for Healthy Living | Healthline. Web. 14 Apr. 2011. <http://www.healthline.com/galecontent/conjoined-twins/2>.

  36. http://www.metacafe.com/watch/122740/baby_born_with_2_heads/

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