PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 391How does a fertilized egg become ananimal?Clam egg and sperm2Developmental Biology is the study of a PROCESS whereby a single cell (the fertilized egg) divides and selectively activates expression of genes to produce a complex organism composed of many cell types. Ex ovo omnia!3To form an embryo, the following (and more!) must occur:• Gametes form and fuse (Reproduction)• Cells multiply (Growth)• Generation of Asymmetry• Axis Determination (Positional information)- Anterior/Posterior (Head-Tail)- Dorsal/Ventral (Back-Front) - Left/Right • Cells differentiate• Structures are built from cells (Morphogenesis)-Animal cells organize into sheets and move-Plant cells form structures without movingWhat kinds of PROCESSES are required?4Differentiation is a central idea of development:All cells have the same DNA, but DIFFERENT CELLS express DIFFERENT GENES5Nature supports an incredible diversity of plant and animal body plans6Yet all of these organisms share conserved developmental mechanisms that are evidence of their evolution from a common ancestor.Our challenge is to understand both this diversity and this unity.7Developmental Biology is studied using the following TOOLS1. Cell Biology2. Genetics3. Molecular Biology8Let’s Review the Basics1. The body is made of millions to billions of cells.2. Cellular machinery is largely made up of proteins3. Because of their different tasks, different cells contain different proteins4. Proteins are made up of chains of amino acids, and these amino acids are "encoded" in the cell's DNA1. Information flows from DNA to RNA to Protein2. When one gene is mutated, one protein is affected (usually disabled).5. All cells have the same DNA but different cells express different genes9Development Occurs at an Unfamiliar ScaleIf a cell was the size of a basketball (8 inches) • a mouse would be the size of Chapel Hill (10 miles) • a gene would be about an inch long.=10Development Occurs at an Unfamiliar ScaleIf a protein was the size of a Volvo (10 feet)• a cell would be the size of Chapel Hill (10 miles)• a gene would be about 1.5 miles long but the strand of DNA would only be a few feet wide.=11TESTS•Exam #3 April 1 (covers March 4-30)•FINAL May 6 (covers April 6-27) •NO make-up exams•Regrade requests must be submitted to your TA within one week of exam12Two Extreme Models for Differentiationfrom the late 1800’s (neither is correct)1. Mosaic development2. Regulative development13 Roux’s landmark experiments with frog embryos: do cells have fixed identities that they can maintain without influence from their neighbors?The Mosaic Development model proposesthat cells become progressively committed to specific cell fates Only half an embryo develops“YES”!Differential segregation of genetic potential?4-cell stageKill 2 cells with a hot needle and allow the remaining 2 cells to develop14Roux’s landmark experimentsFigure 3.16. Destroying (but not removing) one cell of a 2-cell frog embryo results in the development of only half the embryo.15 Driesch’s experiments with sea urchin embryos: do cells have fixed identities that they can maintain without influence from their neighbors?The Regulative Development model proposes that cells retain the ability to adjust their fates in response to their cellular environment (No differential segregation of genetic potential)“NO”!Each cell regulated its development to produce an entire embryo16C. elegans17How do cells know which genes to activate as they go through development? Most organisms use 2 sources of info1. parents2. neighbors18Information from parents:The Cell lineageBut what makes “red” different from “blue” in the first place?Mother cell19Mother cellUnequal localization of "determinants"Cell division transfers determinants to a single daughter cellCells are now different.Segregation of determinantsCell type A Cell type B• mechanism to generate asymmetry and subsequent cellular differentiation• determinants are usually proteins or mRNA. • information (proteins/RNA) can be passed on uniformly, or can be segregated to one of the progeny cells.Information from parents:20Mother cellCell interactions Cell type A• an alternative mechanism to generate asymmetry and subsequent cellular differentiation• cell division places daughter cells in different environments• different environments lead to different cell fatesCell type BCell divisionInformation from neighbors:21Cells don’t have to be inside an animal to communicate with each otherExamples1. Yeast2. Slime mold (Dictyostelium)22"A" cell"alpha" cell• 2 yeast cell types: "A" and "alpha"• only cells of different mating types can mateHOW? each cell type makes a specific signal (factor) and has receptors only for the opposite signal"A" cell"alpha" cell"A" factor"A" factor receptor"alpha" factor receptor"alpha" factorSingle yeast cells talk to each other when they want sex!23These cell-cell signalslead the yeast cells that receive them tomove together, change shapeand ultimately fuse,producing a diploid cell24The slime mold develops into an animal only when it (they?) gets hungry!25The remarkable life cycle of a slime moldcAMP signalSlug/GrexFigure 2.1026Dictyostelium discoideum (slime mold) slug stage27The Cells of the Grex Differentiate28Conclusion: Even cells of the most simple eukaryotic organisms sense their environment, migrate, adhere to each other, differentiate, and interactNow, on to more complicated ones!29Breakthroughs in Modern Biology1. All organisms share similar cellular machinery2. All animals use this machinery in similar ways to direct embryonic development30Model Organisms in Developmental Biology Plants Invertebrates VertebratesWhy use model organisms?What features do they have in common?31Model Organisms: Arabidopsis • Small weed, member of the mustard family• can fit thousands of plants into a small growth room • Short generation time (=time from seed to seed) for a plant: 6 weeks • history--most intensely studied plant for past 15 years, genome sequenced, excellent genetics and
View Full Document
Unlocking...