Axes Development

Question 1

What experiment was done to observe the morphogen activin?

Answer 1

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)

Question 2

What data was found about the experiment observing Xbra expression?

Answer 2

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

Question 3

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

Answer 3

Low; high

Question 4

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

Answer 4

Short-range inducers

Question 5

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

Answer 5

Adding an activated receptor

Question 6

In Xenopus where is the dorsal organizer formed?

Answer 6

The opposite side of the site of sperm entry

Question 7

The sperm enters from which pole of the Xenopus oocyte?

Answer 7

Animal pole

Question 8

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

Answer 8

Cortical rotation

Question 9

What causes cortical rotation and translocation of dorsalizing activity?

Answer 9

Microtubules

Question 10

What is the mechanism of cortical rotation?

Answer 10

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

Question 11

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

Answer 11

b, c, d

Question 12

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

Answer 12

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

Question 13

What ligand is important in stabilizing dorsal blastomeres?

Answer 13

Beta-catenin stabilization through Wnt signaling

Question 14

What is the relation between Wnt11 and dorsalizing activity?

Answer 14

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

Question 15

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

Answer 15

Fast

Question 16

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

Answer 16

Slow

Question 17

What can be done to rescue ventralized embryos?

Answer 17

Transplanting a dorsal vegetal blastomere

Question 18

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

Answer 18

Chordin

Question 19

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

Answer 19

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

Question 20

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?

Answer 20

Six3 in the eyes and Sizzled ventrally

Question 21

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?

Answer 21

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

Question 22

What determines the anterior-posterior patterning in Drosophila?

Answer 22

The position of egg in ovary

Question 23

What are the maternal effect genes in Drosophila ovaries?

Answer 23

Bicoid (anterior) and Nanos (posterior)

Question 24

The maternal effect genes are synthesized by which cells?

Answer 24

Nurse cells

Question 25

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

Answer 25

Asymmetrically

Question 26

Why is mRNA localization important?

Answer 26

Generating asymmetric protein distribution and high local protein concentrations

Question 27

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

Answer 27

b, d, c, a

Question 28

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

Answer 28

Microtubules; oocyte streaming

Question 29

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

Answer 29

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

Question 30

A Bicoid mutant has _________ posterior ends

Answer 30

Two

Question 31

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

Answer 31

Wild type phenotype is rescued

Question 32

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

Answer 32

Head structures are present in the middle

Question 33

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

Answer 33

Two-headed phenotype

Question 34

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

Answer 34

Symmetrically

Question 35

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

Answer 35

Anterior; posterior

Question 36

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

Answer 36

Anterior; posterior

Question 37

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

Answer 37

Gap genes

Question 38

What are some examples of gap genes?

Answer 38

Knirps, giant, Kruppel, tailess

Question 39

Which genes regulate spatial domains of homeotic genes?

Answer 39

Pair-rule genes

Question 40

What are some examples of pair-rule genes?

Answer 40

Eve and Ftz

Question 41

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

Answer 41

Segment-polarity genes

Question 42

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

Answer 42

Homeotic genes