Presentation on theme: "Chapter 1- “The anatomical tradition” ______________- progressive change in multicellular organisms ___________- study of animal development _________________."— Presentation transcript:
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 layers- 1._____________- Outer embryo layer Skin Nerves 2.______________- Inner embryo layer Digestive tract Respiratory system 3._____________- Middle layer Blood Heart Kidney Gonads Bones Connective tissue Muscle Commit these to memory
“Homologous” vs “Analogous” “________________”- 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 Human arm 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)
1.__________- One cell is subdivided into many cells to form a blastula 2. _________________- Extensive cell rearrangement to form endo-, ecto- and meso-derm 3. ____________________- Cells rearranged to produce organs and tissue 4. _________________- produce germ cells (sperm/egg) Note: Somatic cells denote all non-germ cells General Animal Development
The Frog Life cycle Unfertilized egg (Stained) 100’s of fertilized eggs Vegetal pole Animal 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
A unicellular protist The “goo” theory can work! A single cell 3 cm long! What happens if we swap nuclei?? Species 1Species 2 Nucleus (in Rhizoid)
Sexual reproduction Bacteria, amoeba- Reproduction without sex _________________- Sex without reproduction Sex and reproduction are two distinct processes Sex- mixing of genetic material from two individuals Reproduction- creation of new individuals Swap “micronuclei” then separate ________________- Sex with reproduction
Sexual reproduction Asexual reproduction Chlamydomonas (A eukaryote) Fig. 2.8 Chromosome mixing “Plus”“Minus” “Plus”“Minus”
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
Chlamydomonas Gonium Panadorina EudorinaPleodorinaVolvox Single cell Principle 1 : One cell ______________ into 4-64 cells Principle 2 : ___________________ of cell types- somatic vs reproductive 2000 cells Germ cells Somatic cells (appear as dots) Fig. 2.11 Example – Volvox
Principle 3 : _______ cells instructed to perform specific functions Multicellular aggregation to from a slug- Dictystelium >10,000 cell _____________ A _______ is formed (2-4 mm ) Travel to new food source Differentiate into _______ and spore case Stalk dies, spores released Individual cells Start here Fig 2.17 This cycle requires adhesion, _____________ and ______________.
1.________- One cell is subdivided into many cells to form a blastula 2. __________- Extensive cell rearrangement to form endo-, ecto- and meso-derm 3. _____________- Cells rearranged to produce organs and tissue 4. _______________- produce germ cells (sperm/egg) Note: Somatic cells denote all non-germ cells General Animal Development (From chapter 2)
Chapter 3- Experimental Embryology Three major approaches 1.External forces - ____________________ 2.Internal forces- ____________________ 3.Organ development (Morphogenesis) 1. External forces 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 Fig. 3.1 Summer Spring
Chapter 3- Experimental Embryology 2. Internal forces A few definitions ____________________- development of specialized cell types ____________________- developmental fate is restricted Two stages- 1. ___________________- 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) All ___________ do this Fig. 3.11 Transplant cells Normal development Removed cells are compensated Cell fate dictated by location c. Note- insects display __________ Specification- cell fate is determined in egg cytoplasm
Chapter 3- Experimental Embryology 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 A little makes red A modest amount makes white Fig. 3.19 French Flag Analogy Transplanted tissue retain it’s _____________, but differentiates according to new _______________ 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 -But nearby cells will form a limb Salamander If remove limb bud, surrounding cells will form the limb Nematode infection disrupts normal limb field Tree frog Fig. 3.22 2. Internal forces (continued)
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 + endoderm Mesoderm + endoderm +epidermis How do the cells “know” where to go? One model- The ____________ model Malcolm Steinberg 1964
3. Morphogensis (continued) Cells interact so as to form an aggregate with the smallest _________________free energy The _____________ model 20.1 Surface tension 8.5 12.6 4.6 1.6 Fig. 3.30 Adhesion is dictated by 1.Number of cell adhesion molecules 2.Type of cell adhesion molecules In other words, those with stronger _________ properties move to the _________ of a cell mass
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 Cadherins bind to __________in cells, which bind to actin cytoskeleton Fig. 3.31 Catenins Cadherin
3. Morphogensis (continued) ___-cadherin- in all mammalian embryos, then restricted in epithial tissues of embryos and adults Cadherins are responsible for cell sorting Cadherin types Fig. 3.31 Cells with different ___________ sort Cells with different cadherin _____sort ___-cadherin- primarily in placenta ___-cadherin- in mesoderm and developing central nervous system ____-cadherin-required for blastomere adhesion