Chapter 11 Flashcards
“We are standing and walking with parts of our body which could have been used for thinking had they developed in a another part of the body”
Hans Spemann
Xenopus tropicalis (African clawed toad) was chosen due to its:
1) _______ (reaches sexual maturity in 6 months)
2) will _______ instead of only one/year
3) simple _______ genome
1) rapid life cycle
2) reproduce year round
3) diploid
Danio rerio (zebrafish) became a model vertebrate system because:
1) _______ with large broods
2) easily to maintain with _______
3) rapid development
4) first vertebrate in which extensive _______ studies have been done
1) breeds year round
2) transparent bodies
3) mutagenesis studies
Xenopus tropicalis and Danio rerio are used as model systems to study _______ development
vertebrate
Xenopus fertilization can happen anywhere in the _______ hemisphere, and the point of sperm entry determines the _______ side
animal
ventral
After sperm entry, microtubules organized by sperm centriole cause the _______ to rotate 30° with respect to the yolky inner cytoplasm
cortical cytoplasm
Rotation of the cortical cytoplasm exposes the _______, where gastrulation begins
grey crescent
Xenopus cleavage is _______ symmetrical and _______
radially
holoblastic
The presence of _______ inhibits/slows cleavage in the vegetal region
yolk
- animal pole cleavage furrow moves at 1mm/min
- vegetal pole cleavage furrow moves at 0.03mm/min
_______ becomes visible @128 cell stage
blastocoel
- also known as the morula stage
The blastocoel allows for _______ during gastrulation and prevents _______ cells that will become endoderm from prematurely _______ the _______ cells that will form ectoderm and neurons
cell movements
vegetal
contacting
animal
_______ forms 180° opposite sperm entry point
slit-like blastopore
_______: is the zone near the equator where the animal and vegetal meet
marginal zone
_______ cells change shape and initiate invagination of the archenteron
bottle
Animal pole cells _______ to enclose the embryo
epibolize
Marginal cells _______ through the dorsal lip of the blastopore
involute
During Xenopus gastrulation:
1) first cells in are the _______ of the forgut
2) next cells in are the _______ - head mesoderm
3) later cells in are the _______ - will form the notochord
1) pharyngeal endoderm
2) prechordal plate
3) chordamesoderm
_______: movement of cells in the vegetal hemisphere ahead of invaginating cells
vegetal rotation
The blastopore continues to widen and expand vegetally, ultimately forming an entire ring of involuting cells surrounding a small _______ of endodermal precursor cells
yolk plug
In xenopus:
1) Animal cells become _______
2) Vegetal cells become _______
3) internal cells around the equator become _______ cells
1) ectoderm
- skin and neurons
2) endoderm
- gut and associated organs
3) mesenchyme
The _______ forms from ectoderm as instructed by underlying mesoderm that was positioned during the movements of gastrulation
central nervous system
Work done by Hans Spemann and Hilde Mangold demonstrated that the only tissue that was autonomously determined was the _______ cells that was derived from the _______ cytoplasm
dorsal lip
gray crescent
Mangold called the _______ cells and their derivatives the organizer
Dorsal lip
the process of the dorsal lip cells inducing ventral tissue to change fates is called _______
primary embryonic induction
- induce dorsal axis and neural tube
The first sign says you are dorsal. The dorsal signal in Xenopus is _______ accumulation in the _______ center
β-catenin
Nieuwkoop
_______ degrades β-catenin, which is initially found throughout the embryo
glycogen synthase kinase 3 (GSK3)
β-catenin is protected on the dorsal side by what 3 things?
1) Disheveled (Dsh)
2) GSK3 binding protein (GBP)
3) Wnt11
_______ and _______ ride cortical microtubules with Kinesin to the dorsal end of the embryo during/prior to the first cleavage
Disheveled (Dsh)
GSK3-binding protein (GBP)
_______ activates an additional β-catenin protection pathway, preventing β-catenin’s degradation
Wnt11
β-catenin is a TF that associates with other Tf’s specifically _______
Tcf3
In the absence of β-catenin, Tcf3 represses _______ and _______ while in the presence, it will activate them
siamois
twin
Siamois and twin are TF’s required for activating _______ organizing genes
dorsal mesoderm
What are some examples of dorsal mesoderm-activating genes?
1) googsecoid
2) Xlim1
3) Chordin
4) Noggin
5) Follistatin
The second signal say you are mesoderm, Dorsal mesoderm. _______ and _______ encode proteins that induce cells above them to become mesoderm
Vg1
VegT
- part of TGF-β
- maternal vegetally tethered mRNA
_______ activates transcription of activin, derriere, and nodal proteins (Xnr)
VegT
Action, derriere, and nodal proteins (Xnr) can activate _______ which instructs cells to become mesoderm
Xbra (brachyury)
All of these essentially act though the same pathway causing the activation of _______ transcription factor in the mesoderm cells above them
Smad 2/4
The genes of the Organizer are activated by:
- high levels of _______
- high levels of _______ and _______
Smad2/4
siamois and twin
Epidermis is induced via the secretion of a family of proteins called the _______, a powerful _______ signal
bone morphogenic proteins (BMP)
ventralizing
The organizer secretes several BMP inhibitors that protect part of the ectoderm from BMP’s so it can become _______
neural tissue
Smad2/4 + Siamois/Twin induce 3 important BMP inhibitors, what are they?
1) chordin
2) noggin
3) follistatin
The organizer _______ epidermalization of the ectoderm above it by interfering with the actions of _______, providing a safe environment for the formation of neural ectoderm
blocks
BMP
Specificity of neural structures:
Different regions/timing induced different _______
structures
Wnt pathway inhibitors:
_______ binds and blocks BMP’s, Nodal, Xwnt8
cerberus
- all 3 must be blocked for head to form
Wnt pathway inhibitors:
_______ binds Wnt protein in solution, preventing their interaction with receptors
Frzb (frisbee)
Wnt pathway inhibitors:
_______ interferes with wnt receptors (frizzled)
Dickkopf
Wnt pathway inhibitors:
_______ initiates a competitive and interfering intracellular pathway that blocks transduction of the wnt signal
insulin-like growth factor
Combined action of Wnt pathway inhibitors establishes a Wnt gradient that specifies the cells along the _______ axis
anterior/posterior axis
- Wnt = posterior
- no Wnt = anterior
BMP gradient specifies _______ axis
dorsal/ventral
In Danio rerio, Injected antisense RNA molecules used to study gene function are called _______
morpholino antisense
_______ genes: allow determination of gene expression patterns and regulation mechanisms
GFP reporter
Embryos are _______ by small molecules, which allow pharmacological agents to be tested for development effects very easily
permeable
Zebrafish undergo _______ cleavage
discoidal meroblastic
Zebrafish have _______ eggs
telolecithal
What is the organizer in Danio rerio
embryonic shield
