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Unlikely human migration (using sperm/egg technology) Wednesday February 15th, 2017 Class 26 Learning Goals Proliferation (case study: cleavage) Apoptosis (case study: caspase) Migration (case study: gastrulation) • After this class, you should be able to: • Predict a likely cleavage pattern based on adult body plan • Connect logical reasons for apoptosis to potential chemical cues by a cellular signaling pathway • Describe a gastrulating embryo in terms of movements of large numbers of cells Polling Question #1 Part 1: Determinants In the early fly embryo, a maternal determinant is physically anchored to the region of the zygote that will go on to become the anterior of the fly. This molecule is an mRNA ( ) of the bicoid gene. Which is the most likely distribution of the Bicoid protein ( ) in early development? 1. 3. 2. 4. Part 1: Determinants Polling Question #2 An embryo inherited a mutation from the father fly in the bicoid gene that creates an premature stop codon very early in the coding region of this determinant. Where is the Bicoid protein in this new mutant embryo? 1. 3. 2. 4. 5. Part 2: Proliferation Peer Instruction In a few words: What is happening in this organism? Why is this early stage called ‘cleavage’? Besides development, where might we expect to find cell proliferation? Peer Instruction Part 2: Proliferation Explain the mechanism of cleavage in each example. Radial cleavage: Spiral cleavage: Discoidal cleavage: Example: Example: Example: Yolk Superficial cleavage: Example: Cells Yolk Un-separated nuclei Polling Question #3 1. 2. 3. 4. Radial cleavage Spiral cleavage Discoidal cleavage Superficial cleavage Which cleavage pattern is most likely occurring in the development of this organism? Polling Question #2 Part 2: Proliferation Some organisms are under tremendous selective pressure to develop quickly. In these species, which cleavage pattern is most likely? 1. 2. 3. 4. Radial cleavage Spiral cleavage Discoidal cleavage Superficial cleavage Part 2: Proliferation Rapid Cell Division Video Part 3: Apoptosis Peer Instruction Why would an adult multicellular organism intentionally destroy a few of its own cells? How does apoptosis help to develop the structure of this paw? Part 3: Apoptosis Apoptosis Video How is the cell destroyed by apoptosis? 1. The plasma membrane is destroyed lipid by lipid. 2. Caspase is destroyed enzyme by enzyme. 3. The cytoskeleton is destroyed filament by filament. 4. The immune system is destroyed cell by cell. 5. Many kinds of proteins are destroyed. 6. The Electron Transport Chain is disrupted. Which is true of this particular apoptotic pathway? 1. Caspase has a single role in the cell. 2. Apoptotic signaling is an example of positive feedback. 3. The apoptosome is a negative regulator of apoptosis. 4. Destruction of cells requires specific molecular interactions with immune cells. Part 3: Apoptosis Polling Question #3 How is the cell destroyed by apoptosis? 1. 2. 3. 4. 5. 6. The plasma membrane is destroyed lipid by lipid. Caspase is destroyed enzyme by enzyme. The cytoskeleton is destroyed filament by filament. The immune system is destroyed cell by cell. Many kinds of proteins are destroyed. The Electron Transport Chain is disrupted. Part 3: Apoptosis Polling Question #4 Which is true of this particular apoptotic pathway? 1. 2. 3. 4. Caspase has a single role in the cell. Apoptotic signaling is an example of positive feedback. The apoptosome is a negative regulator of apoptosis. Specific molecular interactions with immune cells can help to bring about apoptosis of other cells. Part 4: Migration Gastrulation Videos Sea Urchin Gastrulation Fruit Fly Gastrulation Frog Gastrulation Peer Instruction Part 4: Migration Ectoderm Mesoderm Endoderm Blastocoel Dorsal lip Cross section Blastopore Pre-Gastrulation Whole embryo Initial Gastrulation Blastopore Explain these cell movements in the gastrulation of a frog. Part 4: Migration Ectoderm Mesoderm Endoderm Presumptive gut Cross section Whole embryo What is happening here? Polling Question #5 What cellular developmental process is most dramatic and obvious in frog gastrulation? 1. 2. 3. 4. 5. Differentiation Proliferation Movement Apoptosis Signaling Migration Video This video shows the closure of the dorsal opening in fruit fly development. Which of these are needed for dorsal closure? 1. 2. 3. 4. 5. Psuedopodia Signaling to initiate actin polymerization Adhesion proteins to hold cells together Apoptosis Proliferation of new cells Polling Question #6 This video shows the closure of the dorsal opening in fruit fly development. Based on what you see in this video, which of these are needed for dorsal closure? 1. 2. 3. 4. 5. Psuedopodia Signaling to initiate actin polymerization Adhesion proteins to hold cells together Apoptosis Proliferation of new cells Summary Proliferation Apoptosis Migration Differentiation Signaling For Exam 4: Exam 4: All questions are multiple choice (multiple T/F). We will provide a purple Scantron sheet for you. Concept Questions • • • • Classify each of the following as needing either apoptosis, migration or proliferation for optimum development: – Growing back an amputated limb – Developing a hole in a sheet of cells – Connecting two regions of tissue after a wound – Preventing widespread viral infection – Infecting a host What is the likely cleavage pattern of a sea anemone? A monotreme? A shark species in which the first-born eats the other siblings? A spirochete (this last one is a trick question)? Diagram the progression of molecular information between a death signal from a T-cell and the eventual logical death of the cell. – Why is this a good idea? – What proteins, if mutated, might disable the ability to undergo apoptosis? Describe two different kinds of cellular migration in this video.