COMPETITIVE EXAM MCQs SERIES of LIFE SCIENCES for CSIR-UGC NET/JRF, SLET, GATE, and other entrance tests: DEVELOPMENTAL BIOLOGY – Morphogenesis and Organogenesis in Animals.
Syllabus Outline
- Cell aggregation and differentiation in Dictyostelium.
- Axes and pattern formation in Drosophila, amphibia and chick.
- Organogenesis – vulva formation in Caenorhabditis elegans, eye lens induction, limb development and regeneration in vertebrates.
- Differentiation of neurons, post-embryonic development- larval formation, metamorphosis
- Environmental regulation of normal development.
- Sex determination.
This quiz contains 25 concept-based, most frequently asked MCQs on “DEVELOPMENTAL BIOLOGY – Morphogenesis and Organogenesis in Animals”. Each question has a single correct/most appropriate answer.
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1. During starvation, Dictyostelium amoebae aggregate to form a multicellular slug. Which mechanism ensures that the cyclic Adenosine Monophosphate (cAMP) wave propagates only in one direction?
A) Rapid degradation of extracellular cAMP by phosphodiesterase
B) Depletion of intracellular ATP required for adenylyl cyclase activity
C) Internalisation of G-protein coupled receptors in trailing cells
D) Secretion of Spore Differentiation Factor-2 acting as a receptor antagonist
2. Which molecule primarily induces prestalk cell differentiation in the anterior region of the Dictyostelium slug?
A) High extracellular cyclic Adenosine Monophosphate
B) Differentiation-Inducing Factor-1
C) Ammonia released from posterior cells
D) Spore Differentiation Factor-2
3. During Drosophila oogenesis, Gurken-Torpedo signalling helps establish embryonic axes. Which statement correctly describes this interaction?
A) Gurken is produced by ventral follicle cells and binds Torpedo receptors on the oocyte membrane.
B) Loss of the torpedo gene causes complete dorsalization due to constitutive signalling.
C) Torpedo receptors are localised only in nurse cells and establish the anterior-posterior axis.
D) Gurken protein synthesised near the dorsal oocyte nucleus signals adjacent follicle cells to adopt dorsal fate.
4. A dominant-negative mutation makes the Toll receptor unable to transmit intracellular signals. What phenotype is expected in the embryos?
A) Completely dorsalized embryos because the Dorsal protein cannot enter nuclei
B) Completely ventralized embryos because Cactus is degraded everywhere
C) Embryos with duplicated anterior structures
D) Normal embryos because Torpedo compensates for Toll signalling
5. Which statement correctly describes anterior-posterior axis formation in Drosophila embryos?
A) Bicoid forms an anterior-to-posterior gradient, while Nanos represses hunchback translation in the posterior region.
B) Bicoid forms an anterior-to-posterior gradient, while Nanos represses hunchback translation in the anterior region.
C) Nanos forms an anterior-to-posterior gradient, while Bicoid represses hunchback translation in the anterior region.
D) Nanos forms an anterior-to-posterior gradient, while Bicoid represses hunchback translation in the posterior region.
6. Researchers performed laser ablation experiments during vulva development in C. elegans and obtained the following observations:
I – Removal of the anchor cell produces a vulvaless adult.
II – Removal of all six vulval precursor cells produces a vulvaless adult.
III – Removal of the three central vulval precursor cells causes the outer precursor cells to form vulval tissue.
Which conclusion is correct?
A) The anchor cell acts only as an inducer, while outer precursor cells lack vulval potential.
B) The six vulval precursor cells form an equivalence group, and the anchor cell provides the inductive signal.
C) Central precursor cells inhibit vulval differentiation in outer cells through juxtacrine signalling.
D) Hypodermal cells normally suppress vulval differentiation unless destroyed.
7. What is the primary function of Pax6 during vertebrate eye lens induction?
A) It acts as a secreted morphogen that induces corneal development.
B) It enables the head ectoderm to respond to optic vesicle signals.
C) It prevents premature invagination of the optic cup.
D) It acts as a receptor tyrosine kinase for Fibroblast Growth Factor-8.
8. After the lens vesicle detaches from the surface ectoderm during vertebrate eye development, which reciprocal inductive event occurs next?
A) The lens vesicle induces the optic cup to form neural retina only.
B) The optic stalk induces crystallin synthesis in the lens.
C) The lens vesicle induces ectoderm to differentiate into the cornea.
D) The cornea induces lens fibre differentiation through Dickkopf proteins.
9. In an amphibian embryo, the optic vesicle is surgically removed before contacting the surface ectoderm. What will happen to the overlying ectoderm?
A) It will form a normal lens autonomously.
B) It will differentiate into epidermis instead of lens tissue.
C) It will form an ectopic optic cup.
D) It will differentiate into neural crest cells.
10. During salamander limb regeneration, a specialised epidermal layer forms over the wound surface. This structure is functionally equivalent to which embryonic structure?
A) Zone of Polarising Activity
B) Apical Ectodermal Ridge
C) Progress Zone
D) Somatic lateral plate mesoderm
11. What is the major difference between epimorphic regeneration and morphallactic regeneration?
A) Epimorphosis involves dedifferentiation and proliferation of blastema cells, whereas morphallaxis involves tissue remodelling with minimal cell division.
B) In morphallactic regeneration, new organs develop exclusively from pluripotent stem cells.
C) Epimorphic regeneration occurs without cell proliferation, whereas morphallactic regeneration requires extensive mitosis.
D) Morphallactic regeneration is restricted to vertebrates, whereas epimorphic regeneration occurs in invertebrates.
12. Which experimental manipulation causes truncation of the developing tetrapod limb, resulting in loss of distal structures such as the zeugopod and autopod?
A) Removal of the Zone of Polarising Activity
B) Rotation of the progress zone
C) Surgical removal of the Apical Ectodermal Ridge
D) Removal of dorsal ectoderm
13. Which statement correctly describes the mechanism of thyroid hormone action during metamorphosis in amphibians?
A) Thyroid hormones bind to membrane-bound G-protein-coupled receptors and activate cAMP.
B) Thyroxine is converted into Triiodothyronine, which binds nuclear thyroid hormone receptors, acting as transcription factors.
C) Thyroid hormones activate cytoplasmic proteases that trigger tail degeneration independently of gene expression.
D) Metamorphosis occurs only when Juvenile Hormone levels become higher than thyroid hormone levels.
14. Which hormonal interaction determines whether an insect’s moult produces another larval stage, a pupa, or an adult?
A) The relative levels of ecdysone and Juvenile Hormone
B) The concentration of prothoracicotropic hormone alone
C) Environmental temperature controls ecdysone synthesis
D) Sequential activation of Hox genes in the corpus allatum
15. Certain amphibians, such as the axolotl, exhibit neoteny. What does neoteny mean?
A) Complete absence of a larval stage during development
B) Rapid somatic development compared to reproductive development
C) Retention of larval characters in a sexually mature adult
D) Inability to regenerate lost body parts
16. Which enzyme converts thyroxine into the active hormone triiodothyronine during amphibian metamorphosis?
A) Aromatase
B) Type II deiodinase
C) Cytochrome P450 side-chain cleavage enzyme
D) 5-alpha reductase
17. How does the Sex-lethal gene regulate female development in Drosophila?
A) It acts as a transcription factor regulating double sex expression.
B) It controls sex-specific splicing of transformer pre-mRNA.
C) It degrades male-specific messenger RNAs in the cytoplasm.
D) It phosphorylates the Male Specific Lethal complex.
18. Which environmental factor controls sex determination in many reptiles, such as turtles and crocodiles?
A) Duration of light exposure during embryonic development
B) Lipid content of the egg yolk
C) Salinity of the surrounding environment
D) Incubation temperature during a critical developmental period
19. Which of the following statements are correct regarding the role of dorsal protein in establishing dorsoventral polarity in Drosophila?
I – In embryos lacking Gurken protein, Dorsal protein fails to enter the nuclei of follicle cells, leading to ventralization of the embryo.
II – Although Dorsal acts as a morphogen, it is initially distributed uniformly in the cytoplasm of the syncytial blastoderm embryo.
III – In embryos lacking the Cactus protein, the Dorsal protein enters nuclei throughout the embryo.
A) I and II only
B) I and III only
C) II and III only
D) I, II and III
20. Which of the following statements are correct regarding regeneration?
I – Mammalian liver regeneration is an example of compensatory regeneration.
II – Hair regeneration from follicles represents stem cell-mediated regeneration.
III – Regeneration by tissue remodelling with little cell proliferation is called morphallaxis.
IV – Formation of a blastema from dedifferentiated cells is called epimorphosis.
A) III and IV only
B) I, II and IV only
C) I, II, III and IV
D) IV only
21. Assertion (A): Protein Kinase A activity is essential for terminal differentiation of both prestalk and prespore cells in Dictyostelium.
Reason (R): Spore Differentiation Factor-2 (SDF-2) inhibits adenylyl cyclase activity in all cells of the migrating slug.
A) Both A and R are true, and R correctly explains A
B) Both A and R are true, but R does not correctly explain A
C) A is true, but R is false
D) Both A and R are false
22. Assertion (A): Dorsoventral axis formation in Drosophila depends on the localised distribution of messenger RNA before fertilisation.
Reason (R): The dorsal mRNA is localised specifically at the ventral pole by nurse cells.
A) Both A and R are true, and R correctly explains A
B) Both A and R are true, but R does not explain A
C) A is true, but R is false
D) Both A and R are false
23. Assertion (A): The default fate of vulval precursor cells in C. elegans is hypodermal differentiation.
Reason (R): Removal of the gonad primordium causes all vulval precursor cells to differentiate into hypodermal cells.
A) Both A and R are true, and R correctly explains A
B) Both A and R are true, but R does not correctly explain A
C) A is true, but R is false
D) A is false, but R is true
24. Assertion (A): The Apical Ectodermal Ridge determines whether a limb develops as a wing or a leg.
Reason (R): The Apical Ectodermal Ridge secretes Fibroblast Growth Factor-8, which changes Hox gene expression patterns in mesenchymal cells.
A) Both A and R are true, and R correctly explains A
B) Both A and R are true, but R does not explain A
C) A is true, but R is false
D) Both A and R are false
25. Assertion (A): Distinct puffing patterns appear on polytene chromosomes during insect metamorphosis.
Reason (R): Ecdysone enters cells, binds nuclear receptors, and directly regulates transcription of target genes.
A) Both A and R are true, and R correctly explains A
B) Both A and R are true, but R does not correctly explain A
C) A is true, but R is false
D) A is false, but R is true
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References
- Michael Barresi and Scott Gilbert (2023). Developmental Biology, Oxford University Press, 13th Edition.
- Lincoln Taiz, Ian Max Møller, Angus Murphy, and Eduardo Zeiger (2022). Plant Physiology and Development, Oxford University Press, 7th Edition.
- Geoffrey Cooper and Kenneth Adams (2022). The Cell: A Molecular Approach, Oxford University Press, 9th Edition.
- Alberts, B., Johnson, A., Lewis, J., Morgan, D., Raff, M., Roberts, K., & Walter, P. (2014). Molecular Biology of the Cell, Garland Science, 4th Edition.
- Robert A Weinberg, Robert A. Weinberg (2006). The Biology of Cancer, Taylor & Francis, 1st Edition.
- Gupta, P.K. (2022). Cell and Molecular Biology, Rastogi Publications, 5th Edition.
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