Developmental Bio Test 2

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Developmental Bio Test 2
2013-10-29 20:13:20
Developmental biology

Test 2
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  1. micropylar orifice
    in zebrafish chorion, where sperm enters
  2. zebrafish fertilization and cleavage
    • fertilization is external
    • sperm enters micropylar orifice in chorion, binds to microvilli on egg surface, and fuses with egg
    • cortical granules beneath egg surface exocytose and release their contents = chorion lifts off the egg surface
    • then cytoplasmic streaming happens where the nonyolk cytoplasm moves to the animal pole and forms the cytoplasmic cap
    • first cleavages are vertical = one layer of blastomeres that are connected to yolk mass
    • then a horizontal cleavage = outer layer of blastomeres not connected to yolk cell
  3. cortical granules
    • secretory vesicles containing vitelline membrane components that are released from the egg at fertilization
    • vitelline membrane: extracellular membrane around a zygote
  4. chorion
    extracellular layer surrounding a fish or insect egg
  5. cleavage in zebrafish
  6. blastomeres
    the large cells arising from the fertilized egg by cleavage divisions
  7. mid-blastula transition (MBT)
    • after 9 divisions
    • set of coordinated changes in the late blastula including the onset of zygotic genome transcription
    • cell cycle length increases
    • synchrony of divisions breaks down
    • cells become more motile
    • the outer blastomeres that are connected to the yolk cell sink into it = multi-nuclear syncytium that is thicker around periphery
    • syncytium nuclei divide rapidly 3-4 times
    • rest of yolk cell is surrounded by a thin layer of cytoplasm (no nuclei)
  8. yolk syncytial layer
    • results when the outer blastomeres that were connected to the yolk cell sink into it
    • thicker on periphery of embryo but extends under the blastoderm
  9. blastoderm
    • sheet of cells
    • compare to blastula which is a ball of cells
    • inside consists of deep cells
  10. enveloping layer
    • external layer of epithelial cells generated by the main blastoderm
    • will form the periderm (outer layer) of the larval epidermis
  11. gastrulation
    • brings about the 3 germ layers
    • 3 processes:
    • epiboly:spreading and increase in area of a cell sheet
    • involution: internalization of a cell sheet, carried out by the deep cells
    • convergent extension: cell sheet elongates and narrows
  12. hypoblast/mesendoderm
    lower layer that is formed when the blastoderm begins to involute
  13. germ ring
    involution begins and the blastoderm becomes thicker around the margin
  14. embryonic shield
    • dorsal region of the blastoderm
    • becomes thicker
    • compare to dorsal lip of Xenopus
    • elongates by convergent extension
    • its outer layer becomes the neural plate
  15. Neurulation
    • dorsal ectoderm thickens to form the neural plate
    • neural plate converges toward dorsal midline and then mashes up to form neural keel (rod)
    • secondary cavitation creates a neural tube
    • somites form next to notochord
  16. zebrafish fate maps
    • constructed by labeling early cells and seeing where their descendants end up later
    • constructed right before gastrulation
    • lots of cell mixing
  17. mutagenesis screens
    • identify recessive mutations by breeding for 3 generations
    • point mutations induced with ethyl nitrosourea (ENU) in spermatogonia of the males
    • in F3 generation can get homozygous mutants (but they might die so have to look at them before they do)
    • now better ways to view organs individually: immunostaining, in situ hybridization, GFP
  18. complementation analysis
    • genetic test to find if 2 recessive mutants lie in the same gene by introducing one mutation on the maternal and the other on the paternal chromosome
    • if they are in different genes then the wild-type alleles should complement and show no phenotype
    • if they are in same gene they will fail to complement and a phenotype will result
  19. polyspermy
    fertilization by multiple sperm
  20. acrosome
    golgi-like body in mouse spermcontains enzymes (proteases) that digest through proteins of the follicle cell layer
  21. centriole
    mid-piece in mouse sperm that is rich in mitochondria
  22. capacitation
    period of time when mammal sperm stay in female reproductive tract during which they become competent to fertilize