Axes Development Flashcards
What experiment was done to observe the morphogen activin?
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)
What data was found about the experiment observing Xbra expression?
The higher the dose of activin the further away Xbra gene expression is turned on
Xbra responds to (low/high) concentrations of activin and Gsc responds to (low/high) concentrations of activin
Low; high
What are the molecules that initiate a sequential chain of secondary signals?
Short-range inducers
What experiment can be done to test if a ligand is a morphogen?
Adding an activated receptor
In Xenopus where is the dorsal organizer formed?
The opposite side of the site of sperm entry
The sperm enters from which pole of the Xenopus oocyte?
Animal pole
The sperm entry promotes a phenomenon in Xenopus oocyte. What is it?
Cortical rotation
What causes cortical rotation and translocation of dorsalizing activity?
Microtubules
What is the mechanism of cortical rotation?
Sperm centriole acts as microtubule organizing centre (MTOC; minus end)
Cortex and dorsalizing activity move towards the plus end of microtubules
Which of the following does the cortical rotation include?
a. Cytoplasm
b. Cytoskeletal components
c. ER
d. Plasma membrane
b, c, d
What happens if microtubule polymerization is blocked by UV or MT depolarizing agents?
Cortical rotation and dorsalizing activity do not take place
Embryo is ventralized
What ligand is important in stabilizing dorsal blastomeres?
Beta-catenin stabilization through Wnt signaling
What is the relation between Wnt11 and dorsalizing activity?
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
Dsh and GBP moving along growing end of microtubules by kinesin is a (slow/fast) process
Fast
Wnt11 mRNA moved by cortical rotation to future dorsal side is a (fast/slow) process
Slow
What can be done to rescue ventralized embryos?
Transplanting a dorsal vegetal blastomere
Injection of which molecule inducing organizer can rescue UV phenotype in the embryo?
Chordin
What are other molecules, apart from Wnts, beta-catenin and Chordin, can rescue UV-ventralized phenotype?
Noggin (BMP antagonist) and nodal-related proteins (TGF-beta pathway)
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?
Six3 in the eyes and Sizzled ventrally
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?
BMP morpholino represses ventral side, no Sizzled expressed
Chordin morpholino represses dorsal side, overexpression of Sizzled
What determines the anterior-posterior patterning in Drosophila?
The position of egg in ovary
What are the maternal effect genes in Drosophila ovaries?
Bicoid (anterior) and Nanos (posterior)
The maternal effect genes are synthesized by which cells?
Nurse cells
Bicoid and nanos are (symmetrically/asymmetrically) distributed in the egg
Asymmetrically
Why is mRNA localization important?
Generating asymmetric protein distribution and high local protein concentrations
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
b, d, c, a
Bicoid is transported on ____________ to the anterior end and nanos is transported by __________ ____________ to the posterior end
Microtubules; oocyte streaming
How is the anterior-posterior asymmetric gradient in Drosophila formed?
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
A Bicoid mutant has _________ posterior ends
Two
If Bicoid mRNA is injected to the anterior end of Bicoid mutant, what happens?
Wild type phenotype is rescued
If Bicoid mRNA is injected in the middle part of Bicoid mutant, what happens?
Head structures are present in the middle
If Bicoid mRNA is injected to the posterior end of wildtype Bicoid, what happens?
Two-headed phenotype
Maternal effect genes Hunchback and Caudal are (asymmetrically/symmetrically) distributed in the egg
Symmetrically
Bicoid inhibits translation of caudal mRNA at the ____________ end and nanos prevents translation of hunchback mRNA at the _____________ end
Anterior; posterior
Hunchback mRNA is concentrated at the __________ end and caudal mRNA is concentrated at the __________ end
Anterior; posterior
Which genes are associated with mutations that cause gaps in segmentation pattern?
Gap genes
What are some examples of gap genes?
Knirps, giant, Kruppel, tailess
Which genes regulate spatial domains of homeotic genes?
Pair-rule genes
What are some examples of pair-rule genes?
Eve and Ftz
Which genes turn on homeotic gene expression and define segment identity along the AP axis?
Segment-polarity genes
Which genes control the pattern of body formation during early embryonic development?
Homeotic genes
