Developmental Bio Test 2

  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
Card Set
Developmental Bio Test 2
Test 2