Zoo 470 Spring 2015 Page i Lectures 1 2 Dates W 1 21 15 F 1 23 15 Introduction What Is Developmental Biology Key Terms Wonder cool Epigenesis preformation Differentiation morphogenesis pattern formation Experimental embryology Gastrulation fate mapping induction Organizer Germ layer ectoderm mesoderm endoderm Sufficiency necessity Autonomous specification localized determinants mosaic development Conditional specification regulative development Model system organism Fluorescence microscopy green fluorescent protein GFP Learning Objectives By the end of this unit you should be able to 1 Explain how epigenesis and preformation rightly understood underlie our modern understanding of developmental biology 2 Define the terms differentiation morphogenesis and pattern formation and explain why they are key ideas in developmental biology 3 Define germ layer and the three basic types of tissues that form in embryos during development 4 Based on classic examples explain how fate mapping and microsurgery can be used to examine what influences are required for correct differentiation of a cell tissue 5 Describe the basic Spemann Mangold Organizer experiment and how it demonstrates that the organizer produces inductive signals 6 Explain how experimental embryology can be used to investigate mechanisms of differentiation 7 Explain the difference between necessity and sufficiency and explain in a general sense what is required to show each in an embryological experiment 8 Explain the term autonomous specification and cite one or more specific examples 9 Explain the classical concept of mosaic development and how localized determinants may explain this phenomenon 10 Explain the term conditional specification and the classical concept of regulative development and cite one or more examples 11 Explain the new ways of analyzing embryos that have been made possible in the modern era of molecular developmental biology including advances in the use of model systems genetics and microscopy 12 Recognize that developmental biology raises ethical issues regarding human persons that biology cannot answer Reading assignment Gilbert 10e Ch 1 pp 1 11 12 19 Part II pp 107 113 Gilbert 9e Ch 1 pp 1 11 12 19 Part II pp 109 116 Zoo 470 Spring 2015 Page ii Introduction What is Developmental Biology A Developmental Biology What Is It 1 The motivation for studying biology in general and developmental biology in particular wonder Albert Einstein The most beautiful thing we can experience is the mysterious It is the source of all true art and science He to whom this emotion is a stranger who no longer pauses to wonder and stand rapt in awe is as good as dead David Psalm 139 For Thou didst form my inward parts Thou didst weave me in my mother s womb I will give thanks to Thee for I am fearfully and wonderfully made wonderful are Thy works and my soul knows it very well My frame was not hidden from Thee when I was made in secret skillfully wrought in the depths of the earth Thine eyes have seen my unformed substance and in Thy book they were all written the days that were ordained for me when as yet there was not one of them 2 The central problem of developmental biology how do parts become different a Tools and model organisms are central to the rise of modern developmental biology b Epigenesis vs preformation a chicken and egg problem c Differentiation The process by which differing properties are conferred on parts of the embryo at different times and in specific locations such that specialized structures arise in a reliable fashion in the mature organism d Morphogenesis How form Greek arises e Pattern formation How different parts become highly ordered spatially f Spemann the video A classic case study B Developmental Biology Big Ideas Gilbert 7e Fig 10 21 1 Review from the video a Fate mapping Vogt a cell s ancestry is sometimes crucial for its differentiation and behavior and we need to know that ancestry in detail to interpret disruption experiments Zoo 470 Spring 2015 Page iii b Germ layers Primary tissue types established during development including i ectoderm outer forms epidermis and neural tissue ii mesoderm middle forms muscle blood notochord somites etc and iii endoderm inner forms gut many organ systems Gilbert 10e Fig 1 7 c Organizer Spemann Mangold sends signals to surrounding tissues but remembers its own fate when placed in a new environment d Induction the process by which one cell or tissue the inducer sends a signal to a second cell or tissue the induced tissue resulting in a specific and reproducible change in its differentiation 2 What Experiments Tell Us a Sufficiency and necessity Sufficiency When a group of cells or molecule when added to a cell embryo or tissue confers the ability to differentiate in a particular way Does NOT mean a molecule or group of cells is necessary Example Bill Gates vs the lottery If a cell or molecule is sufficient but not necessary this often indicates functional redundancy Necessity When a group of cells or molecule is removed from a cell embryo or tissue the ability to differentiate in a particular way is lost Does NOT mean a molecule or group is sufficient Example Air and water If something is necessary but not sufficient it indicates it acts together with other essential cells molecules b Specification the extent to which a cell or tissue will differentiate normally when placed into a new surrounding Autonomous specification to thine own self be true e g E B Wilson and mosaic development in mollusks differentiation occurs as it would in the intact embryo See Gilbert 10e Fig P2 1 Zoo 470 Spring 2015 Page iv It often involves localized determinants Example ascidians Gilbert 10e Fig 1 12 Gilbert 10e Fig P2 3 Gilbert 10e Fig P2 2 Conditional specification the differentiation of a cell or tissue depends on its local environment Example Hans Driesch and sea urchins Gilbert 10e Fig P2 7 Zoo 470 Spring 2015 Page v C Developmental Biology Modern Approaches a Model systems have continued to be keys to unlocking the mechanisms of differentiation and morphogenesis b Cellular control of development Judith Kimble s dictum Developmental biology is cell biology over time c Molecular and genetic control of development Studying genes their function and regulation example homeotic genes D Developmental Biology Societal Implications 1 Ethical issues arise from science but aren t solved by science Examples cloning and stem cells 2 Really important questions this course will raise