BIO412_C1.pdf

BIO412/712 Animal Developmental Biology Introduction: 08/08/2024 A framework for understanding animal Ram Sambasivan development Multicellular animal builds itself from a single cell Development -...

BIO412/712 Animal Developmental Biology Introduction: 08/08/2024 A framework for understanding animal Ram Sambasivan development Multicellular animal builds itself from a single cell Development - slow progressive change Building the body: between fertilisation and birth -the developing organism - embryo Neonate to adult A neonate is a newborn baby, or a child under 28 days of age. The first 28 days of a child's life are called the neonatal period. Adult until death Questions: Cell differentiation? Single cell to 100s of functional cell types How various cell types form? How do they differ from one another figure 1.7 The dividing cells of the fertilized egg form three distinct embryonic germ layers. Each of the germ layers Single cell sequencing - a revolution gives rise to myriad differentiated cell types (only a few representatives are shown here) and distinct organ systems. The germ cells (precursors of the sperm and egg) are set aside early in development and do not arise from any particular germ layer. Morphogenesis? How cells organise into tissues and organs? How tissues and organs spatially pattern to create an ordered form? - Cell proliferation, cell migration, cell shape changes, cell death - Tissue reorganisation - folding, tube formation, segmentation Growth? Single cell to billions of cells How right size is achieved? Reproduction? Germ cell biology Information carried to make next generation Regeneration? Skin / blood / gut; Wear and tear or Injury repair Environmental integration? Sex determination; Drugs and pollutants- disruption of development Evolution? Changes in development to new body forms Course structure Introduction: Molecular and cellular mechanisms underlying animal development Early development: How different cell types form from a single cell? How the blueprint for the form of animal body is laid out? Recent advances: studying human development Organogenesis: How do tissues and organs form? How are they patterned? Integrating development with medicine, ecology and evolution: Developmental defects Recent advance: organoids to model disease Developmental underpinning of evolutionary changes The cycle of life Animals and plants develop through embryos figure 1.1 Developmental history of the leopard frog, Rana pipiens. The stages from fertilization through hatching (birth) are known collectively as embryogenesis. The region set aside for producing germ cells is shown in purple. Gametogenesis, which is completed in the sexually mature adult, begins at different times during development, depending on the species. (The sizes of the varicolored wedges shown here are arbitrary and do not correspond to the proportion of the life cycle spent in each stage.) Learned from classic embryology Cleavage stage Rapid division of zygote to make large number of cells - 50,000 cells in 12 hrs - drosophila Nuclear to cytoplasmic ratio restored quickly Achieved by abolishing gap phases of cell cycle - G1 and G2 Not random divisions generating a clump of cells Pattern of cell divisions lays the foundation for next steps and thus, for animal body plan Patterns of cleavage Gilbert / Barresi  Cleavage pattern of taxa- inherited Yolk imposes constraints figure 1.5 provides a classification of cleavage types and shows the influence of yolk on cleavage symmetry and pattern. Gilbert / Barresi  Gastrulation - overview Gastrulation is what makes animals animals Cells of blastula acquire new position, new neighbours Generates the body plan of animals Germ layers formed Ectoderm (Outer) Endoderm (Inner) Mesoderm (Middle) Body axes established Anterior-posterior axis (head-tail or mouth-anus) Dorsal-ventral axis (back-belly) Left-right lateral sides Vertebrate development Evaluation pattern 30 - Quiz 1, 2 30 - Mid Semester 40- End Semester