Bioe 20B W4D1 - Oct 22 Annotated Slides PDF

REMINDERS ANNOUNCEMENTS 1. Today: Development Tuesday, 10/22/24 2. Due Sunday: HW 4, Quiz 4, Methods Flow Chart 3. Midterm 1 is on Thursday, October 24th Week 4, Day 1 Midterm content: Form and Function, Energetics and Development Part 1...

REMINDERS ANNOUNCEMENTS 1. Today: Development Tuesday, 10/22/24 2. Due Sunday: HW 4, Quiz 4, Methods Flow Chart 3. Midterm 1 is on Thursday, October 24th Week 4, Day 1 Midterm content: Form and Function, Energetics and Development Part 1 Metabolism, Nutrition and Digestion, Osmoregulation, Circulation, Respiration, Nervous System Format: Individual, similar to practice exam TODAY’S AGENDA (8-9:35AM) Animal Fun Fact of the Day (Part 1) Development Part 1 5 min break Kahoot: Cell Potency Midterm Review (if time permits) DEVELOPMENT EXTREMES IN NATURE Animal Fun Fact of the Day Flatworms (planarians) can be cut up into multiple pieces each of which regenerates into a new worm! Can you guess how many pieces? 279! Development  Learning Goals for Today 1 Stages of Development & Differential Gene Expression 2 Fate or Luck? How is cell fate determined? 3 What is the role of genes in development 4 How do genes generate patterns 5 Can you ever go back? Reversing cell differentiation, stem cells REVIEW: Big Picture What is development? Process by which a multicellular organism progresses from a fertilized egg to a mature adult sperm + egg = zygote blastocoel 32-cell stage gastrulation REVIEW: Big Picture How does the genetic code get translated into a 3-dimensional being? Vocabulary terms: Cell Potency = Totipotent à pluripotent à multipotent à unipotent Not determined determined Determination = Setting the fate of the cell Differentiation = Becoming a particular cell type All cells have whole genome but only a Differential Gene Expression = subset of genes are expressed/transcribed in each cell type Gene Cascade = One set of transcriptions turns on next set of transcription factors  Learning Goals for Today 1 Stages of Development & Differential Gene Expression 2 Fate or Luck? How is cell fate determined? 3 What is the role of genes in development 4 How do genes generate patterns 5 Can you ever go back? Reversing cell differentiation, stem cells REVIEW: Cell potency Undifferentiated cell’s potential to become a cell of a specific type Totipotent (all capable) Any cell type (i.e. embryos) Pluripotent (many capable) Most cells types besides embryos (i.e. embryonic stem cells) Multipotent (several capable) several related cell types (i.e. adult stem cells) Unipotent (one capable) only its same cell type (i.e. somatic cells) REVIEW: Cell potency Identify the cell potency of each: Not determined Embyo Embryonic stem cell Adult stem cell Determined Somatic cells REVIEW: Cell potency w h a t ’s y ? t ’s p la Le o te n c y ? t ce ll p tha  Learning Goals for Today 1 Stages of Development & Differential Gene Expression 2 Fate or Luck? How is cell fate determined? 3 What is the role of genes in development 4 How do genes generate patterns 5 Can you ever go back? Reversing cell differentiation, stem cells REVIEW: Determination vs. Differentiation Determination Differentiation Process of setting cell fate Process of actually becoming a cell (i.e. blueprint) (i.e. construction) cytoplasmic segregation Differential Gene Expression All cells have the same genome but different induction genes are turned on in different cell types Gene Cascade One set of genes turns on the next set of genes, and so forth (i.e. dominoes) REVIEW: Cell determination and differentiation (specific to muscle cells) MyoD is a protein encoded by the Myoblast determining gene that serves as a transcription factor in differentiating muscle cells. REVIEW: Mechanisms that lead to Differential Gene Expression Cytoplasmic segregation – Induction – (mRNAs or proteins) (via proximity) unequal cytokinesis; some factor is Cell to cell communication; a unevenly distributed within the cytoplasm factor is made and transported to (asymmetry) induce other cells to differentiate Mother/parent cell 2 Daughter cells Gene A Gene A not turned on turned on REVIEW: Mechanisms that lead to Differential Gene Expression REVIEW: Induction: A spatial signal (cell-cell communication based on proximity) The concentration gradient of the inducer extending out from the signaling cell is critical At some threshold, the signal transduction pathway is triggered and the transcription factor moves to nucleus or is otherwise activated REVIEW: Mechanisms that lead to Differential Gene Expression What mechanism of DGE is this an example of? This is an example of cytoplasmic EXAMPLE: P granules in c. elegans segregation Strome Lab, UCSC (DGE via asymmetry) P granules are involved in determining the germ line (cells that will become egg or sperm) Are separated into just a few cells REVIEW: Mechanisms that lead to Differential Gene Expression What mechanism of DGE is this an example of? REVIEW: Morphogens are a type of inducer Morphogen = Diffusible substance whose concentration gradient determines a developmental pattern blue (signaling protein) white red The French Flag Model Lewis Wolpert, 1969 REVIEW: Morphogens are a type of inducer Morphogen example = Sonic Hedgehog (Shh) Concentration of Shh = [Shh] Morphogen secreted from Low [Shh] Zone of Polarizing Activity High [Shh] Low [Shh] High [Shh] Fig. 19.11 REVIEW: Morphogens are a type of inducer A baby is born with a normal thumb and a second finger partially converted into a thumb. A plausible explanation is that the cells that were going to become the second finger received A. too much Shh. B. not enough Shh. How would this look graphically? High [Shh] (concentration) Low [Shh] [Shh] protein index middle ring Thumb Pinkie (phenotype) REVIEW: Morphogens are a type of inducer You are a researcher studying the formation of a unique (and newly discovered!) color pattern (rainbow) in the wings of drosophila (see image below). You identify a molecule that you think may be acting as a morphogen to make this color pattern. (gene suppressed/absent) In your experiments, you find that when you knock out the gene for this morphogen, the wing pattern is absent and the wing is all purple. Given this information, draw a graph that depicts a hypothesis for how this morphogen results in the rainbow phenotype. Write a brief explanation for your graph below. Wildtype Concentration of Morphogen (normal) High [R] Low [Shh] Mutant Phenotype Low [Shh] High [R]  5-min Break! Attendance Time Scan the QR code or go to https://tinyurl.com/Oct22W4D1 to answer the following question: 1) What is the difference between gene determination and differentiation? (This will be used for taking attendance today.)  Learning Goals for Today 1 Stages of Development & Differential Gene Expression 2 Fate or Luck? How is cell fate determined? 3 What is the role of genes in development 4 How do genes generate patterns 5 Can you ever go back? Reversing cell differentiation, stem cells REVIEW: Genes and pattern formation Complex patterns are formed by a cascade of transcription factors released in a specific sequence & which form morphogen gradients In Drosophila (head) (rear) (back) (belly) Maternal Effects Genes – anterior posterior (and dorsal ventral) axis (i.e. bicoid, nanos, hunchback) Segmentation Genes – boundaries and polarity of each segment Hox Genes – which organ will be made at given location REVIEW: Morphogens in drosophila à maternal effects gene mRNA (from mom) BICOID NANOS Bicoid = Bring it on! (promotes Bicoid/Nanos effect translation of hunchback) Translated to protein translation of Nanos = Nope! (inhibits translation hunchback protein of hunchback) HUNCHBACK Head (Anterior) Tail (Posterior) REVIEW: Morphogens in drosophila Hunchback promoted by bicoid Hunchback inhibited by nanos Draw the final concentration gradient for hunchback Head because hunchback promoted No head because hunchback inhibited Head (Anterior) Tail (Posterior) REVIEW: Morphogens in drosophila REVIEW: Maternal effects genes On your boards… 1) On the first set of axes, draw a graph of the concentration of bicoid, nanos, and hunchback mRNA after all mRNA has been transported to its final location. 2) On the second set, draw a graph of the concentration of the PROTEINS of bicoid, nanos and hunchback. Before After [mRNA] [protein] Anterior Posterior Anterior Posterior REVIEW: Genes and pattern formation à promotes hunchback in anterior SCENARIO: If there was a mutation in the BICOID gene in a mother fruit fly (Drosophila) what would be the result in the offspring? On your boards, draw what the fruit fly offspring would look like if it were able to get all the nutrients it could to survive to adulthood. REVIEW: Genes and pattern formation SCENARIO: In one mutant fly, there are legs where the antennas should be and in another fly there are an extra pair of wings in place of legs. What could explain these mutations? Mutation in HOX genes à which organs are made at a given location Genes to form antenna Genes to form leg are Genes to form legs are Genes to form wings are turned on turned on turned on are turned on  Learning Goals for Today 1 Stages of Development & Differential Gene Expression 2 Fate or Luck? How is cell fate determined? 3 What is the role of genes in development 4 How do genes generate patterns 5 Can you ever go back? Reversing cell differentiation, stem cells REVIEW: Reversing differentiation via Stem Cells rapidly dividing undifferentiated cells that can Stem Cells – differentiate into diverse cell types What are the current or future uses of stem cells? Organ repair or replacement Tissue repair or replacement Cancer treatments Cloning of valuable animals/endangered species REVIEW: Reversing differentiation via Stem Cells What are the 2 ways we get pluripotent stem cells? 1) Embryonic Stem Cells (ESCs) – Group of cells in the blastocyst of mice and humans; can give rise to most cell types but not new organism 2) Induced Pluripotent Stem Cells (iPS) – induce adult skin cells back to an undifferentiated state; can make many cell types Avoids controversy Avoid immune system problems from introducing “non-self” tissue into another individual Concept Maps Online Study Tool: coggle  Review at home by creating a concept map for the following terms, add your own terms too! Differential gene expression Differentiation Determination Morphogen Apoptosis Form and function Mutation Cytoplasmic segregation Induction Add your own ideas