CSIR NET Life Sciences Developmental Biology Syllabus

Developmental Biology syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Developmental Biology in CSIR NET Life Sciences, not a summary of it.

1. 1

   Basic concepts of development

   13 topics

   • Potency
   • Commitment
   • Specification
   • Induction
   • Competence
   • Determination
   • Differentiation
   • Morphogenetic gradients
   • Cell fate and cell lineages
   • Stem cells
   • Genomic equivalence and the cytoplasmic determinants
   • Imprinting
   • Mutants and transgenics in analysis of development
2. 2

   Gametogenesis, fertilization and early development

   11 topics

   • Production of gametes
   • Cell surface molecules in sperm-egg recognition in animals
   • Embryo sac development and double fertilization in plants
   • Zygote formation
   • Cleavage
   • Blastula formation
   • Embryonic fields
   • Gastrulation and formation of germ layers in animals
   • Embryogenesis
   • Establishment of symmetry in plants
   • Seed formation and germination
3. 3

   Morphogenesis and organogenesis in animals

   3 topics

   • 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
     • Environmental regulation of normal development
     • Sex determination
4. 4

   Morphogenesis and organogenesis in plants

   5 topics

   • Organization of shoot and root apical meristem
   • Shoot and root development
   • Leaf development and phyllotaxy
   • Transition to flowering
   • Floral meristems and floral development in Arabidopsis and Antirrhinum
5. 5

   Programmed cell death, aging and senescence

   overview

   Examined as a single unit within Developmental Biology — no further topic split in the official outline.

Developmental Biology flashcards for CSIR NET Life Sciences

25 of 54 cards from the Developmental Biology deck — real questions with worked answers.

1. Define 'potency' in developmental biology and name the levels in order of decreasing potency.

   Potency is the total range of cell types a cell can give rise to. In decreasing order: totipotent (forms entire organism incl. extra-embryonic, e.g. zygote) > pluripotent (all three germ layers, e.g. ICM cells) > multipotent (cells within one lineage, e.g. hematopoietic stem cell) > oligopotent > unipotent (single type).

2. Distinguish 'specification' from 'determination' (commitment).

   Specification is a reversible early commitment: a cell will follow a fate if placed in a neutral environment but can still be respecified by changing its surroundings. Determination is irreversible, stable commitment: the cell follows its fate even when transplanted to a different (non-neutral) environment.

3. What is 'commitment' and what are its two sequential states?

   Commitment is the process by which a cell becomes restricted to a particular developmental fate. Its two states are specification (labile/reversible) followed by determination (fixed/irreversible).

4. Define 'induction' and name the two interacting tissues involved.

   Induction is the process where one group of cells (the inducer/inducing tissue) signals to and changes the developmental fate of an adjacent group (the responding tissue). It requires a signal from the inducer and competence in the responder.

5. What is 'competence' in the context of embryonic induction?

   Competence is the ability of a responding tissue to perceive and respond to an inductive signal. It is acquired and lost over a defined time window, so the same signal produces different effects depending on when it is received.

6. Differentiate instructive induction from permissive induction.

   In instructive induction the signal determines which fate the responding tissue adopts (different signals give different outcomes). In permissive induction the responder is already specified and the signal merely allows/enables it to express its predetermined fate.

7. What is 'differentiation' and does it usually involve changes in the genome?

   Differentiation is the process by which cells become structurally and functionally specialized through differential gene expression. It generally does NOT involve loss or change of genome (genomic equivalence is retained); specialization arises from which genes are expressed.

8. Define a 'morphogen' and state how it specifies different cell fates.

   A morphogen is a diffusible signaling molecule produced from a localized source that forms a concentration gradient. Cells respond to different threshold concentrations by expressing different genes, so a single gradient specifies multiple fates in a position-dependent (concentration-dependent) manner.

9. State the 'French Flag model' and what it explains.

   The French Flag model (Wolpert) explains positional information: a morphogen gradient across a field of cells, with two concentration thresholds, divides the field into three regions (blue/white/red) each adopting a distinct fate based on local morphogen concentration.

10. Distinguish 'cell fate' from 'cell lineage'.

    Cell fate is what a cell will normally become during normal development (mapped by fate maps). Cell lineage is the ancestral pedigree—the complete sequence of cell divisions tracing a cell back to its progenitor (e.g. the invariant lineage of C. elegans).

11. What is the principle of 'genomic equivalence' and which classic experiment demonstrated it?

    Genomic equivalence states that all somatic cells of an organism contain the same complete genome despite differentiating differently. It was demonstrated by Gurdon's nuclear transplantation in Xenopus (a differentiated intestinal cell nucleus into an enucleated egg produced a normal frog) and by cloning of Dolly the sheep.

12. What are 'cytoplasmic determinants' and how do they direct cell fate?

    Cytoplasmic (morphogenetic) determinants are maternally provided molecules (mRNAs/proteins) localized unequally in the egg cytoplasm. During cleavage they are partitioned into different blastomeres, giving them distinct fates—this is the basis of autonomous (mosaic) specification.

13. Compare mosaic (autonomous) development with regulative (conditional) development.

    Mosaic development relies on cytoplasmic determinants partitioned during cleavage; each blastomere is determined early and isolated blastomeres form only partial embryos (e.g. Ctenophores, ascidians). Regulative development relies on cell-cell interactions; isolated blastomeres can form a whole embryo (e.g. mammals, sea urchin, amphibians).

14. Define 'genomic imprinting' and give a classic example pair.

    Genomic imprinting is parent-of-origin-specific gene expression, where only the maternal OR paternal allele is expressed due to differential epigenetic (DNA methylation) marks. Examples: Igf2 (paternally expressed) and H19 (maternally expressed); Prader-Willi (loss of paternal) vs Angelman (loss of maternal) syndromes.

15. What are stem cells, and what two defining properties do they have?

    Stem cells are undifferentiated cells with two key properties: (1) self-renewal—they divide to make more stem cells, and (2) potency—they can differentiate into one or more specialized cell types. Division is often asymmetric (one stem + one differentiating daughter).

16. Distinguish embryonic stem (ES) cells from adult (somatic) stem cells in potency.

    ES cells are derived from the inner cell mass of the blastocyst and are pluripotent (can form all three germ layers). Adult stem cells reside in tissues and are typically multipotent/unipotent, restricted to lineages of their tissue (e.g. hematopoietic, mesenchymal stem cells).

17. What are induced pluripotent stem (iPS) cells and which four factors classically reprogram them?

    iPS cells are differentiated somatic cells reprogrammed to a pluripotent state. The classic Yamanaka factors are Oct4, Sox2, Klf4, and c-Myc (OSKM).

18. How are transgenic organisms and gene knockouts used to analyze development?

    Transgenics introduce or overexpress genes (gain-of-function) to test sufficiency; knockouts/knockdowns (loss-of-function via targeted mutation, RNAi, or CRISPR) test necessity. Mutant analysis (e.g. Drosophila saturation mutagenesis screens) identifies genes controlling developmental pathways and their epistatic order.

19. Outline gametogenesis: how do spermatogenesis and oogenesis differ in product number per primary cell?

    Spermatogenesis: one primary spermatocyte → meiosis → 4 functional, equal-sized motile sperm; continuous, with cytoplasmic reduction. Oogenesis: one primary oocyte → 1 large functional ovum + 2-3 polar bodies (unequal cytoplasmic division), arrested in meiosis, with stockpiling of cytoplasm.

20. Describe the acrosome reaction in sperm-egg recognition in animals.

    On contact with the egg's outer coat (jelly/zona), the sperm acrosome (a lysosome-derived vesicle) undergoes exocytosis, releasing hydrolytic enzymes that digest the coat and exposing acrosomal proteins (e.g. bindin) that allow species-specific binding and fusion with the egg membrane.

21. Name the molecules mediating sperm-egg recognition in sea urchin and in mammals.

    Sea urchin: bindin on the sperm binds species-specific bindin receptor (EBR1) on the egg vitelline layer. Mammals: sperm proteins (e.g. Izumo1) bind egg receptor Juno; the zona pellucida glycoprotein ZP3 acts as the primary sperm receptor and triggers the acrosome reaction.

22. What are the fast and slow blocks to polyspermy?

    Fast block: rapid membrane depolarization of the egg (Na+ influx) within seconds prevents additional sperm fusion (in sea urchin). Slow block (cortical reaction): Ca2+ wave triggers cortical granule exocytosis, raising the fertilization envelope/hardening the zona (zona reaction, ZP2 cleavage), permanently blocking polyspermy.

23. Describe embryo sac (female gametophyte) development in angiosperms (Polygonum type).

    A megaspore mother cell undergoes meiosis to give 4 megaspores; 3 degenerate. The functional megaspore undergoes 3 mitotic divisions producing an 8-nucleate, 7-celled embryo sac: 1 egg + 2 synergids (egg apparatus at micropylar end), 3 antipodal cells (chalazal end), and 1 central cell with 2 polar nuclei.

24. Explain 'double fertilization' in flowering plants and its two products.

    Two sperm cells delivered by the pollen tube: one fuses with the egg to form the diploid (2n) zygote; the other fuses with the two polar nuclei of the central cell to form the triploid (3n) primary endosperm nucleus, which develops into the nutritive endosperm.

25. What molecular and structural events define zygote formation (egg activation) immediately after fertilization?

    Sperm-egg fusion triggers a Ca2+ release wave that activates the egg: completion of meiosis, cortical reaction, increased protein synthesis and metabolism, fusion of male and female pronuclei (karyogamy/amphimixis) to restore diploidy, and initiation of DNA replication for first cleavage.

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