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73 Cards in this Set
- Front
- Back
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Strongylocenrotus purpuratus |
Sea Urchin |
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embryo (sea urchin) |
radial cleavage (deuterostome) |
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gastrula |
formed through gastrulation |
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pleuteus |
free swimming larvae- bilateral symmetry |
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hans driech experiements |
4 cell embryo- each as competent to form a complete (but smaller) embryos -2-to-4 cell embryo could undergo regulative development |
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whatis lost at the 8 cell stage? |
regulative potential |
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gene regulatory networks |
little change in body plan since early cambrian Eric Davidson (Caltech) -complex networks of genetic interactions driving embryo development |
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kernels of development |
inflexible subcircuts that are essential functions in development =highly conserved, if function is lost, its lethal for the embryo |
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ascidians |
C. Intestinalis (ie. sea squirt) |
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Ciona intestinalis |
Ascidian |
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urochordate |
has a notochord and neural tube durng development but no vertebrae possess a notochord, neural tube, and body muscle similar to early vertebrae development |
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hermaphrodite |
possesses both female oocyctes and male sperm, eggs are fertilized externally |
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embryo (Ascidian) |
invarient cleavage pattern |
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tadpole (Ascidian) |
motile larval stage, similar to vertebrate embryos |
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metamorphosis (Ascidian) |
tadpole changes into sac-like adult |
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invarient cleavage |
-in early embryo -cleave in the exact same way |
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regulative and mosaic development in ascidians |
regulative separation of two cell embryo- two small complete embryo mosaic- muscle cells specified at 8 cell stage by cytoplasmic determinants
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cytoplasmic determinants (myoplasm) |
asymmetric distribution of protein in egg - determined muscle fate |
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chordates |
have a vertebral column |
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vertebral column |
– segmented backbone surrounding the spinal cord • brain at head end enclosed in a skull (bone or cartilage) |
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A-P axis |
main body axis of vertebrates – head, trunk with pairs appendages (limbs or fins), posterior end tail |
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D-V axis |
– back to belly – spinal cord dorsal, mouth ventral |
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bilateral symmetry |
– A-P and D-V axis create symmetry at the dorsal midline - right and left sides are mirror images (lungs, kidneys and gonads) • Left-right asymmetry - heart (left) and liver (right) |
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phylotypic stage |
• All chordate embryos pass through the phylotypic stage - when embryos are similar in appearance • common features: head, notochord, neural tube (earlies appearance of nervous system), somites (blocks of mesoderm) |
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gametogenesis |
development/genesis of gametes (oocytes/sperm) |
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fertilization |
union of sperm and egg |
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cleavage |
earliest cell division, rapid cell division through which embryo becomes divided into smaller cells |
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gastrulation |
dynamic process through which three germ layers (ectoderm, mesoderm. Endoderm) organize themselves |
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notochord formation |
column of mesoderm located just ventral to neural tube |
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neurulation |
formation of the neural tube – precursor to nerve cord (runs along dorsal midline along A-P axis) |
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somitogenesis |
formation of regularly spaced blocks of mesoderm (somites) flanking notochord that give rise to skeleton and muscle |
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organogenesis |
development of organs and tissues (internal organs, eyes, limbs ect.) |
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Xenopus laevis development |
• Studies initiated in the mid 1980’s - basis for what we know about early development of the embryo • Hundred of fertilized eggs easy to obtain • Embryos are large (scale bar 0.5mm) – allowed for dissection of the early embryo • Dissected tissues easy to culture • Not a good genetic model (tetraploid) – duplication of diploid genome in evolutionary h |
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fertilization (Xenopus) |
union of sperm and egg, sperm enters animal region of egg |
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cleavage (Xenopus) |
to form blastula, blastomeres= individual cell of blastula 1st cleavage: along A/V axis, divides egg in left-right halves – cleavage about every 20 minutes 2nd cleavage: 90 degrees to first cleavage 3rd cleavage: equatorial and asymmetric - four small animal and four large vegetal, 8 blastomere |
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neural tube formation (Xenopus) |
neurulation |
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neurlation (Xenopus) |
the process in which the ectoderm of the future brain and spinal cord develops folds that come together to form the neural tube |
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neurula (Xenopus) |
stage of vertebrate development at the end of gastrulation when the neural tube is forming |
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organogenesis (Xenopus) |
development of organs and issues |
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tailbud embryo (Xenopus) |
phylotypic stage, body has developed and neural tube, somites, notochord, and head strucutres present |
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egg (Xenopus) |
has a distinct polarity |
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animal-vegetal axis |
vegetal region of the egg contains the contents of the yolk, the animal region doesnt |
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zygote |
diploid, formed after fertilization |
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blasulation |
formation of blastula/blastomeres |
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blastula stage: |
reached after 12 divisions(~4096 cells) |
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radial symmetry |
(no visible sign of A/P or D/V axis) |
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blastocoel |
a fluid filled cavity in animal region |
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marginal zone |
– equatorial ring around embryo separating animal and vegetal region |
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ectoderm (Xenopus egg) |
animal region |
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mesoderm (Xenopus egg) |
marginal zone |
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endoderm (Xenopus egg) |
marginal zone, vegetal region |
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gastrula stage |
formation of blastopore (dorsal lip) first sign of dorsal/ventral polarity and begin of gastrula stage |
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gastrulation |
the morphogenic process occurring in three dimensions where endoderm and mesoderm are internalized |
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blastopore |
a small slit like infolding of marginal zone on dorsal side |
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dorsal lip |
blastopore |
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involution of embryo |
mesoderm and endoderm enter the blastopore and migrate (via involution) to the future anterior of the embryo – germ layers migrate as a coherent sheet of cells - first tissues to enter the embryo are most anterior • ventral side initiates involution after dorsal side – delayed but similar cell movements occur on ventral side |
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epiboly |
ectoderm spreads to cover the whole embryo |
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archenteron |
a second cavity forms during gastrulation (future gut cavity) - blastocoel reduces in size |
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lateral mesoderm |
(mesoderm the spread to the left and right of the midline) spreads ventrally to cover inside of archenteron. |
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embryonic/Spemann organizer
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the mesoderm contacts both the ectoderm and endoderm along its anterior/posterior length and mesoderm is patterned along its anterior/posterior axis |
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neurula stage |
neurulation |
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neurulation |
formation of the neural tube |
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neural tube |
precursor to CNS -edge of the neural plate forms neural folds which rise towards midline and fuse to form neural tube -the neural tube sinks below epidermis. • the anterior neural tube becomes brain - middle and posterior neural tube becomes spinal cord. |
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notochord |
(rod along dorsal midline) |
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somites |
(segmented blocks of mesoderm along notochord) |
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lateral plate mesoderm |
will form mesoderm derived organs (i.e. heart (A) kidneys (P)) becomes heart, kidney, gonads and gut muscles. • ventral mesoderm blood-forming tissues. |
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neural plate |
the ectoderm located above notochord and somites |
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neural folds |
edge of the neural plate forms neural folds |
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tailbud stage |
after neurulation |
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forebrain, midbrain, and hindbrain |
the brain (anterior neural tube) divided into three parts |
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organogenesis |
eyes and ears start to develop |
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branchial arches |
– form jaws |
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neural crest cells |
come from the edges of the neural folds after neural tube fusion - they detach and migrate as single cells between the mesodermal tissues to become sensory and autonomic nervous systems, pigment cells and some cartilage of skull |
