Flash card

Developmental Biology

  • Focus: Study of how organisms grow and develop, including cellular differentiation and morphogenesis.

Embryology

  • Definition: Study of embryos and their development.

  • First known embryologist: Aristotle.

Main Stages of Embryology

  1. Fertilization

    • Definition: Fusion of sperm and egg to form a zygote.

    • Differentiated cells involved: Spermatozoon and oocyte.

  2. Gametogenesis

    • Process: Formation of gametes via meiosis.

    • Precursor cells: Primordial germ cells.

  3. Cell Division

    • Mitosis: Cell division producing identical daughter cells.

      • Stages: Interphase, Prophase, Metaphase, Anaphase, Telophase (IPMAT).

      • Chromosome behavior: Duplication and separation.

    • Meiosis: Reductional division producing gametes with half the chromosome number.

      • Stages: Meiosis I and II, with IPMAT stages in each.

  4. Cleavage

    • Definition: Rapid mitotic division of the zygote.

    • Products: Blastomeres.

    • Embryonic stages: Morula → Blastula (Blastocyst in humans).

  5. Gastrulation

    • Process: Formation of the three germ layers (ectoderm, mesoderm, endoderm).

    • Results: Gastrula stage and differentiation into tissues and organs.

  6. Organogenesis and Morphogenesis

    • Organogenesis: Formation of organs.

    • Morphogenesis: Development of the body's shape and structure.

  7. Metamorphosis

    • Definition: Transformation from larva to adult.

    • Examples: Frogs, butterflies.

  8. Comparative Embryology

    • Methods of birth:

      • Oviparity: Egg-laying (e.g., birds).

      • Viviparity: Live birth (e.g., mammals).

      • Ovoviviparity: Eggs hatch inside the mother (e.g., some reptiles).

Original Theories of Development

  • Epigenesis: Gradual development.

  • Preformation: Organisms preformed in miniature form.

Mechanisms of Cellular Diversity

  • Processes: Differentiation, induction, pattern formation, morphogenesis, growth, reproduction, regeneration, environmental integration, evolution.

  • Factors affecting morphogenesis:

    • Cell division, shape changes, migration, growth, apoptosis, membrane composition.

Processes in Development

  • Apoptosis: Programmed cell death; importance in tissue shaping.

  • Senescence: Cellular aging; significance in development and disease.

Embryonic Observation Techniques

  • Fate maps: Track cell lineage.

  • Dye marking: Visualize cells.

  • Genetic labeling: Create chimeric embryos for lineage tracking.

Transgenic DNA Chimeras

  • Definitions: Transgenic organisms and chimeras.

  • Creation: Genetic modification techniques.

Evolutionary Embryology

  • Charles Darwin: Contributions to embryology and evolution.

  • Embryonic homologies:

    • Homologous structures: Similar origins (e.g., vertebrate limbs).

    • Analogous structures: Similar functions but different origins (e.g., wings of bats and insects).

Genetic Malfunctions and Disruptions

  • Causes: Syndromes, teratogens.

Unit 2: Cell Specification

Stages of Commitment

  1. Labile specification: Reversible cell identity.

  2. Determination: Irreversible cell fate.

Modes of Specification

  • Autonomous: Internal factors.

  • Conditional: External signals.

  • Syncytial: Shared cytoplasm; common in insects.

Morphogens

  • Role: Establish polarity and organogenesis.

  • Examples: Bicoid and nanos in insects.

Unit 3: Sex Determination and Gametogenesis

Sex Determination

  • Chromosomal:

    • Mammals: XY (male), XX (female).

    • Birds, Drosophila, Bonellia viridis: Variations.

  • Environmental:

    • Temperature (reptiles), location (Bonellia viridis).

Gametogenesis

  1. Spermatogenesis:

    • Location: Seminiferous tubules of testes.

    • Steps: Spermatogonia → Primary spermatocytes → Secondary spermatocytes → Spermatids → Spermatozoa.

  2. Oogenesis:

    • Location: Ovaries.

    • Steps: Oogonia → Primary oocyte → Secondary oocyte → Ootid → Ovum.

Unit 4: Stem Cells and Commitment

Types of Stem Cells

  • Totipotent: All cell types (zygote).

  • Pluripotent: Most cell types (inner cell mass).

  • Multipotent: Limited range (hematopoietic stem cells).

  • Unipotent: Single cell type.

Morphogenesis and Cell Adhesion

  • Cadherins: Proteins mediating cell adhesion.

    • Types: E-cadherins, P-cadherins, N-cadherins.

    • Function: Anchor cells during tissue formation.

Unit 5: Environmental Developmental Biology

Environmental Influences

  • Polyphenism, developmental plasticity.

  • UV radiation effects, developmental symbiosis.

Unit 6: Developmental Genetics

Gene Expression Regulation

  • Genomic equivalence evidence.

  • Tools: PCR, somatic nuclear transfer.

  • Gene anatomy: Promoters, enhancers, silencers.

Unit 7: Cell-Cell Communication

Signaling Pathways

  • Paracrine vs. juxtacrine.

  • Pathways: JAK-STAT, RTK, Wnt, Hedgehog, FGF.

Unit 8: Fertilization

Key Concepts

  • Gamete structure and functions.

  • Acrosome reaction, prevention of polyspermy.

  • Capacitation and hyperactivation.

  • Mitochondrial inheritance: Maternal origin.

  • Sperm motility: Essential for navigating the female reproductive tract to reach the ovum.