Chapter 11 Flashcards by evan kang

“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

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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

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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

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Xenopus tropicalis and Danio rerio are used as model systems to study _______ development

vertebrate

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Xenopus fertilization can happen anywhere in the _______ hemisphere, and the point of sperm entry determines the _______ side

animal
ventral

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After sperm entry, microtubules organized by sperm centriole cause the _______ to rotate 30° with respect to the yolky inner cytoplasm

cortical cytoplasm

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Rotation of the cortical cytoplasm exposes the _______, where gastrulation begins

grey crescent

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Xenopus cleavage is _______ symmetrical and _______

radially
holoblastic

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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

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_______ becomes visible @128 cell stage

blastocoel
- also known as the morula stage

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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

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_______ forms 180° opposite sperm entry point

slit-like blastopore

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_______: is the zone near the equator where the animal and vegetal meet

marginal zone

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_______ cells change shape and initiate invagination of the archenteron

bottle

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Animal pole cells _______ to enclose the embryo

epibolize

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Marginal cells _______ through the dorsal lip of the blastopore

involute

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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

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_______: movement of cells in the vegetal hemisphere ahead of invaginating cells

vegetal rotation

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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

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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

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The _______ forms from ectoderm as instructed by underlying mesoderm that was positioned during the movements of gastrulation

central nervous system

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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

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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