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ANAT 381 Experimental Embryology > Axes Development > Flashcards

Axes Development Flashcards

1
Q

What experiment was done to observe the morphogen activin?

A

Co-culture of animal cap and vegetal part of Xenopus blastula
Inject activin mRNA to the vegetal part
Monitor the expression of brachyury (transcription factor Xbra)

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2
Q

What data was found about the experiment observing Xbra expression?

A

The higher the dose of activin the further away Xbra gene expression is turned on

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3
Q

Xbra responds to (low/high) concentrations of activin and Gsc responds to (low/high) concentrations of activin

A

Low; high

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4
Q

What are the molecules that initiate a sequential chain of secondary signals?

A

Short-range inducers

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5
Q

What experiment can be done to test if a ligand is a morphogen?

A

Adding an activated receptor

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6
Q

In Xenopus where is the dorsal organizer formed?

A

The opposite side of the site of sperm entry

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7
Q

The sperm enters from which pole of the Xenopus oocyte?

A

Animal pole

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8
Q

The sperm entry promotes a phenomenon in Xenopus oocyte. What is it?

A

Cortical rotation

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9
Q

What causes cortical rotation and translocation of dorsalizing activity?

A

Microtubules

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10
Q

What is the mechanism of cortical rotation?

A

Sperm centriole acts as microtubule organizing centre (MTOC; minus end)
Cortex and dorsalizing activity move towards the plus end of microtubules

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11
Q

Which of the following does the cortical rotation include?
a. Cytoplasm
b. Cytoskeletal components
c. ER
d. Plasma membrane

A

b, c, d

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12
Q

What happens if microtubule polymerization is blocked by UV or MT depolarizing agents?

A

Cortical rotation and dorsalizing activity do not take place
Embryo is ventralized

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13
Q

What ligand is important in stabilizing dorsal blastomeres?

A

Beta-catenin stabilization through Wnt signaling

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14
Q

What is the relation between Wnt11 and dorsalizing activity?

A

Wnt11 RNA is localized at the vegetal pole
Dispersed from cortex during initial cleavage stage
Wnt11 is translated and secreted from dorsal vegetal cells
Beta-catenin is stabilized

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15
Q

Dsh and GBP moving along growing end of microtubules by kinesin is a (slow/fast) process

A

Fast

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16
Q

Wnt11 mRNA moved by cortical rotation to future dorsal side is a (fast/slow) process

A

Slow

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17
Q

What can be done to rescue ventralized embryos?

A

Transplanting a dorsal vegetal blastomere

18
Q

Injection of which molecule inducing organizer can rescue UV phenotype in the embryo?

A

Chordin

19
Q

What are other molecules, apart from Wnts, beta-catenin and Chordin, can rescue UV-ventralized phenotype?

A

Noggin (BMP antagonist) and nodal-related proteins (TGF-beta pathway)

20
Q

In the experiment where embryos at the 4-cell stage were cultured and underwent in situ hybridization, which molecules were found in the eyes and ventrally?

A

Six3 in the eyes and Sizzled ventrally

21
Q

Each cell of a 4-cell Xenopus embryo was injected with morpholinos against BMP4 or Chordin. What were the results for the cells treated with BMP4 and Chordin morpholinos?

A

BMP morpholino represses ventral side, no Sizzled expressed
Chordin morpholino represses dorsal side, overexpression of Sizzled

22
Q

What determines the anterior-posterior patterning in Drosophila?

A

The position of egg in ovary

23
Q

What are the maternal effect genes in Drosophila ovaries?

A

Bicoid (anterior) and Nanos (posterior)

24
Q

The maternal effect genes are synthesized by which cells?

A

Nurse cells

25
Q

Bicoid and nanos are (symmetrically/asymmetrically) distributed in the egg

A

Asymmetrically

26
Q

Why is mRNA localization important?

A

Generating asymmetric protein distribution and high local protein concentrations

27
Q

Place the steps of mRNA localization in order
a. RNA particle becomes anchored at destination
b. Recognition of cis-acting sequences in mRNA
c. RNA transport particles must be trafficked in the cytoplasm
d. RNA-protein complexes must be packaged into transport particles

A

b, d, c, a

28
Q

Bicoid is transported on ____________ to the anterior end and nanos is transported by __________ ____________ to the posterior end

A

Microtubules; oocyte streaming

29
Q

How is the anterior-posterior asymmetric gradient in Drosophila formed?

A

Bicoid is a RBP and DBP that binds to 3’UTR and represses translation of Caudal
Nanos binds to 3’UTR and represses translation of Hunchback

30
Q

A Bicoid mutant has _________ posterior ends

A

Two

31
Q

If Bicoid mRNA is injected to the anterior end of Bicoid mutant, what happens?

A

Wild type phenotype is rescued

32
Q

If Bicoid mRNA is injected in the middle part of Bicoid mutant, what happens?

A

Head structures are present in the middle

33
Q

If Bicoid mRNA is injected to the posterior end of wildtype Bicoid, what happens?

A

Two-headed phenotype

34
Q

Maternal effect genes Hunchback and Caudal are (asymmetrically/symmetrically) distributed in the egg

A

Symmetrically

35
Q

Bicoid inhibits translation of caudal mRNA at the ____________ end and nanos prevents translation of hunchback mRNA at the _____________ end

A

Anterior; posterior

36
Q

Hunchback mRNA is concentrated at the __________ end and caudal mRNA is concentrated at the __________ end

A

Anterior; posterior

37
Q

Which genes are associated with mutations that cause gaps in segmentation pattern?

A

Gap genes

38
Q

What are some examples of gap genes?

A

Knirps, giant, Kruppel, tailess

39
Q

Which genes regulate spatial domains of homeotic genes?

A

Pair-rule genes

40
Q

What are some examples of pair-rule genes?

A

Eve and Ftz

41
Q

Which genes turn on homeotic gene expression and define segment identity along the AP axis?

A

Segment-polarity genes

42
Q

Which genes control the pattern of body formation during early embryonic development?

A

Homeotic genes

ANAT 381 Experimental Embryology (24 decks)

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