Transcript Chapter 1-3
Chapter 1- “The anatomical tradition” • ______________- progressive change in multicellular organisms • ___________- study of animal development • _________________ = development + embryology Big questions • • • • What dictates _________________? How can cells form ordered ___________? How are _________ cells set apart? How do cells know when to stop _____________? • How do cells know where to ___________? Historical setting Pre-1800s - Two theories 1. ___________ theory– All organs prefigured, but very small – Backed by science, religion, philosophy 2. ______________ – All organs made de novo (from scratch) •Early 1800s- staining techniques/microscopy disprove preformation theory•The birth of “_______________” •Late 1800s- _______ (instead of goo) theory recognized Fate mapping- the mapping of cell lineage Strange terminology • _____________- Organisms with three primary germ layers • _______________- lack a true mesoderm • Hydra, jellyfish, sponges • ________________- Cells receiving cues from other cells Four Principles“Von Baer’s laws” 1. ___________features appear prior to ______________ ones – All vertebrates have gill arches, notochords, primitive kidneys 2. Less general characters are developed from _______ general (i.e. specialized from non-specialized) – Scales vs. feathers – Legs vs. wings – Nails vs. claws 3. An embryo does not pass through the ___________________ of other, lower creatures 4. Thus, the early embryo of a higher animal in never like a lower animal, but only like it’s ___________________. – Humans never look like ____________ Fate mapping Major layers1. _____________• • • Outer embryo layer Skin Nerves 2. ______________• • • Inner embryo layer Digestive tract Respiratory system 3. _____________• • • • • • • • Middle layer Blood Heart Kidney Gonads Bones Connective tissue Muscle “Homologous” vs “Analogous” Human arm • “________________”Similarity arising from a common ancestral structure – e.g. bird wing and human arm • “_______________”Similar function, but not common ancestor – e.g. bird wing and insect wing Seal limb Bird wing Bat wing Teratology • Environmental agents causing disruption of development -called “________________” • Example- __________________ (1961) Chapter 2- Life cycles • All animals follow similar life cycle – __________________- mixing of genetic material between sperm and egg – ___________________- events between fertilization and hatching (or birth) General Animal Development 2. _________________- 1. __________- One cell is subdivided into many cells to form a blastula Extensive cell rearrangement to form endo-, ecto- and meso-derm 4. _________________- produce 3. ____________________- Cells germ cells (sperm/egg) Note: Somatic cells denote all non-germ cells rearranged to produce organs and tissue The Frog Life cycle Animal pole 100’s of fertilized eggs Unfertilized egg (Stained) Vegetal pole Single egg, early blastula Note: Cells get smaller, but egg ___________ remains the same! The Frog Life cycle- gastrulation through neurula 1. _______________________________ forms at “belly” 2. Dorsal blastopore lip becomes the ____________ (a circle) 3. Ectoderm cells encase 4. Mesoderm cells migrate inside along blastopore edges 5. Neural folds and groove appear Fig. 2.3 The Frog Life cycle- metamorphosis A unicellular protist The “goo” theory can work! Species 1 A single cell 3 cm long! Nucleus (in Rhizoid) Species 2 What happens if we swap nuclei?? Sexual reproduction Sex and reproduction are two distinct processes •Sex- mixing of genetic material from two individuals •Reproduction- creation of new individuals •Bacteria, amoeba- Reproduction without sex •_________________- Sex without reproduction Swap “micronuclei” then separate •________________- Sex with reproduction Chlamydomonas (A eukaryote) “Plus” “Minus” Asexual reproduction Sexual reproduction Chromosome mixing “Plus” “Minus” Fig. 2.8 Unicellular eukaryotes have basic developmental processes observed in higher organisms •Mitosis and meiosis is accomplished •Sexual reproduction •Chromosomal structure is stable and similar But, multicellular organisms are a whole new ball game These require cell-cell communication and distinct cell functions “_________________________________” Example – Volvox Example – Volvox Principle 1 : One cell ______________ into 4-64 cells Single cell Chlamydomonas Gonium Panadorina 2000 cells Somatic cells (appear as dots) Germ cells Eudorina Pleodorina Volvox Fig. 2.11 Principle 2 : ___________________ of cell typessomatic vs reproductive Multicellular aggregation to from a slug- Dictystelium Principle 3 : _______ cells instructed to perform specific functions Travel to new food source A _______ is formed (2-4 mm ) Fig 2.17 >10,000 cell _____________ This cycle requires adhesion, _____________ and ______________. Differentiate into _______ and spore case Stalk dies, spores released Individual cells Start here General Animal Development (From chapter 2) 1. ________- One cell is subdivided into many cells to form a blastula 2. __________- Extensive cell rearrangement to form endo-, ecto- and meso-derm 4. _______________- produce germ 3. _____________- Cells rearranged cells (sperm/egg) Note: Somatic cells denote all non-germ cells to produce organs and tissue Chapter 3- Experimental Embryology • Three major approaches 1. External forces - ____________________ 2. Internal forces- ____________________ 3. Organ development (Morphogenesis) 1. External forces Fig. 3.1 a. Sex determination •Boellia- depends on where larva lands •Alligator egg temperature - <30C = _________ development b. Embryo ______________ •Butterflies- colors depend in season •Frogs and UV light Summer Spring Chapter 3- Experimental Embryology 2. Internal forces A few definitions ____________________- development of specialized cell types ____________________- developmental fate is restricted Two stages1. ___________________- capable of becoming specific cell types, but decision is reversible 2. __________________- non-reversible cell fate decision a. __________________specification- blastomere cell fate is determined at blastula stage (e.g. isolated blastomere will become same type if removed from blastula) Most ________________ do this Chapter 3- Experimental Embryology 2. Internal forces (continued) b. ______________ specification- cell fate is determined on where a cell finds itself (e.g. isolated blastomere will become what surrounding cells dictate) Transplant cells All ___________ do this Normal development c. Note- insects display __________ Specificationcell fate is determined in egg cytoplasm Cell fate dictated by location Removed cells are compensated Fig. 3.11 Chapter 3- Experimental Embryology 2. Internal forces (continued) More definitions__________- soluble molecule that instructs cells to differentiate Concentration ___________- A morphogen at different concentrations depending on location of cell Example of concentration gradient- the flatworm (Hydra) It grows back! The French flag analogy to understand gradients 2. Internal forces (continued) A lot makes blue French Flag Analogy A modest amount makes white A little makes red Transplanted tissue retain it’s _____________, but differentiates according to new _______________ Fig. 3.19 2. Internal forces (continued) An example of a concentration gradient- Activin levels dictate cell fate in Xenopus Activin levels Fig. 3.20 2. Internal forces (continued) A _________________ field- a group of cells whose position and fate are specified with respect to the same set of boundaries. •The general fate of a cell group (e.g. tissue) is determined, but individual cells within that tissue can respond to new positional cues Example- a “_______ field” -Transplantation of cells specified for limb development results in limb formation in new place Tree frog -But nearby cells will form a limb Salamander If remove limb bud, surrounding cells will form the limb Fig. 3.22 Nematode infection disrupts normal limb field 3. Morphogensis Morphogenesis is the bigger question of how cells within a given organ are in a precise place and have a precise function. 1. How are _________formed from populations of cells? 2. How are __________ constructed from tissues? 3. How do organs form in particular ____________, and how do migrating cells reach their destinations? 4. How do organs and their cells grow, and how is growth ____________________ throughout development? 5. How do organs achieve ____________? Compare leg and finger cross-sections- the same yet different. 3. Morphogensis (continued) Observations- Mix cells from different cell types in a culture dish, they migrate to pre-instructed location. Mesoderm + epidermis Mesoderm Mesoderm + endoderm + endoderm +epidermis How do the cells “know” where to go? One modelThe ____________ model Malcolm Steinberg 1964 3. Morphogensis (continued) Surface tension The _____________ model 20.1 Cells interact so as to form an aggregate with the smallest _________________free energy 12.6 In other words, those with stronger _________ properties move to the _________ of a cell mass Adhesion is dictated by 1. Number of cell adhesion molecules 2. Type of cell adhesion molecules 8.5 4.6 1.6 Fig. 3.30 3. Morphogensis (continued) _____________ – Calcium-dependent adhesion proteins - a major class of proteins that mediate cell adhesion •Establish intercellular connections •Required for _____________ segregation •Required for organization of animal formation Cadherin Cadherins bind to __________in cells, which bind to actin cytoskeleton Catenins Fig. 3.31 3. Morphogensis (continued) Cadherin types ___-cadherin- in all mammalian embryos, then restricted in epithial tissues of embryos and adults ___-cadherin- primarily in placenta ___-cadherin- in mesoderm and developing central nervous system ____-cadherin-required for blastomere adhesion Cadherins are responsible for cell sorting Cells with different cadherin _____sort Cells with different ___________ sort Fig. 3.31