The following statements regarding the generation of dorsal/ventral axis in Drosophila was made: A. Gurken protein moves along with the oocyte nucleus and signals follicle cells to adopt the ventral fate. B. Maternal deficiencies of either the gurken or torpedo gene cause ventralization of the embryo. C. Gurken is active only in the oocyte and Torpedo is active only in the somatic follicle cells. D. The Pipe protein is made in the dorsal follicle cells. E. The highest concentration of Dorsal is in the dorsal cell nuclei, which becomes the mesoderm. Which one of the following combination of the above statements is true?
B and C
Drosophila Dorsal/Ventral Axis Formation
The formation of the dorsal/ventral axis in the Drosophila embryo is a classic example of developmental signaling involving communication between the oocyte and surrounding follicle cells.
Analyzing Statements on Dorsal/Ventral Axis
Let's examine each statement given in the question:
- A. Gurken protein moves along with the oocyte nucleus and signals follicle cells to adopt the ventral fate.
This statement is incorrect. Gurken protein is produced by the oocyte and localizes dorsally, near the nucleus. It signals to the overlying follicle cells, instructing them to adopt a dorsal fate, not a ventral one. - B. Maternal deficiencies of either the gurken or torpedo gene cause ventralization of the embryo.
This statement is correct. Gurken is the ligand produced by the oocyte, and Torpedo is the receptor (an EGF receptor) found on the follicle cells. Gurken-Torpedo signaling establishes the dorsal fate in the follicle cells. If either Gurken or Torpedo is deficient, this dorsal signal is lost, and all follicle cells adopt the default ventral fate. This results in the entire embryo developing ventral characteristics, a phenomenon known as ventralization. - C. Gurken is active only in the oocyte and Torpedo is active only in the somatic follicle cells.
This statement is correct. Gurken is transcribed and translated within the oocyte. Torpedo, its receptor, is expressed on the surface of the somatic follicle cells that surround the oocyte. This interaction between a ligand from the germline (oocyte) and a receptor on the soma (follicle cells) is crucial for setting up the axis. - D. The Pipe protein is made in the dorsal follicle cells.
This statement is incorrect. Pipe protein is a key factor in establishing the ventral fate. It is expressed and active in the ventral follicle cells, not the dorsal ones. Gurken signaling to dorsal follicle cells prevents Pipe expression/activity in those cells. - E. The highest concentration of Dorsal is in the dorsal cell nuclei, which becomes the mesoderm.
This statement is incorrect. The Dorsal protein acts as a morphogen and its nuclear concentration determines cell fate along the dorsal/ventral axis. The highest concentration of nuclear Dorsal is found in the ventral cell nuclei. High nuclear Dorsal activates genes that specify the mesoderm fate in the ventral region of the embryo. In the dorsal region, Dorsal protein is largely retained in the cytoplasm, resulting in low or absent nuclear concentration, which allows for dorsal fates (like amnioserosa) to form.
Identifying True Statements
Based on the analysis, statements B and C are true statements regarding the generation of the dorsal/ventral axis in Drosophila.
Statement B: Maternal deficiencies of either the gurken or torpedo gene cause ventralization of the embryo.
Statement C: Gurken is active only in the oocyte and Torpedo is active only in the somatic follicle cells.
Therefore, the combination of statements B and C is true.
Important Questions from Morphogenesis and organogenesis in animals
The individuals considered in this question are having two haploid sets of autosomes and no Y- chromosome. The X∶A ratio of the individuals, the type of organisms chosen, their primary sex and number of Barr bodies expected in their cells are shown in the table below:
X∶A ratio Organism Primary Sex Number of Barr bodies i. 0.5
ii. 2
A. Human
B. Drosophila
I. Male
II. Female
III. Metafemale
a. Zero
b. One
c. Two
d. Three
Select the option below with all correct matches:
Several marine organism release their gametes into the environment, where sperm attraction and subsequent events lead to successful fertilization. With reference to sea urchins, which one of the following statements is NOT true?
During wing development in chick, if Apical Ectodermal Ridge (AER) is removed, the limb development ceases, on the other hand placing leg mesenchyme directly beneath the wing AER, distal hindlimb structures develop at the end of the wing, and if limb mesenchyme is replaced by non-limb mesenchyme beneath AER, the AER regresses. This may demonstrate that:
A. the limb mesenchyme cells induce and sustain AER.
B. the mesenchyme cells specify the type: wing or limb.
C. the AER is responsible for specifying the type: wing or limb.
D. the AER is responsible for sustained outgrowth and development of the limb.
E. the AER does not specify the type: wing or limb.
Which combination of above statements is demonstrated by the experiment?
The following statements are made regarding the amphibian early-embryonic development:
A. The Nieuwkoop center cells are mesodermal in origin.
B. Chordin, Noggin and Goosecoid are secreted by the Organizer.
C. The default fate of the ectoderm is to become neural tissue.
D. BMP levels are high in the presumptive dorsal mesoderm.
Which one of the following options represents the combination of all correct statements?
The hedgehog pathway is extremely important in vertebrate limb development, neural differentiation and facial morpho-genesis. In accordance with the above statement, what would happen in mice that are homozygous for a mutant allele of sonic hedgehog (shh)?
