Gene-Regulation-and-Development:基因调控和发育课件.ppt
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- Gene Regulation and Development 基因 调控 发育 课件
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1、Gene Regulation and DevelopmentMaking of the Complex Living things In the development of multicell organisms,a single-cell zygote gives rise to many different cell types.Each type has different structure,under taking different chemical and biologic reactions and performs corresponding functions.All
2、these events are controlled by sets of genes in the cell and influenced by surrounding stimuli.Body system of multicell organisms Cells of similar types are organized into tissues Tissues with associated function into organs Organs of associated function into organ systems Organ systems coordinately
3、 to support the whole organism Process of embryonic development must give rise not only to the cells of different types but also to higher-level structures and coordinated functions.How life begin An organism arises from a fertilized egg as the result of three interrelated processes:cell division,ce
4、ll differentiation,and cell morphogenesis.During development,cells becomes polarized,starts divide unevenly,reprograms gene expression and become specialized in structure and function,a process called differentiation.The processes of morphogenesis is forming of shapes,give cells,tissues and organs t
5、heir proper shape to fit their corresponding functions.All these processes are part of development.Fertilization results in a zygote and triggers embryonic developmentPlasma membraneTailMiddlepieceNeckHeadNucleusAcrosomeMitochondrion(spiral shape)The spermapproachesthe egg1234The spermsacrosomal enz
6、ymesdigest the eggs jelly coatProteins on thesperm head bindto egg receptors5The spermnucleus enters the egg cytoplasmThe plasma membranesof sperm and egg fuse6A fertilizationenvelope formsSPERMNucleusAcrosomePlasmamembraneSpermheadAcrosomalenzymesJellycoat(Zona Pellucida)VitellinelayerPlasmamembran
7、eCytoplasmEGG CELLReceptor proteinmoleculesSpermnucleusEggnucleus7The nucleiof spermand egg fuseZygotenucleusCleavage startsFertilizationof ovumOviductSecondaryoocyteOvulationOvaryBlastocyst(implanted)EndometriumUterusENDOMETRIUMInner cell massCavityTrophoblastBlastocystAntibody against Oct4Trophobl
8、astEggSpermBlastocystEmbryoEmbryonic stem-cellcultureInner cellmassOnce sperm and egg cell fuse(zygote),cell start to divide and differentiate.The first differentiated structure:a blastocyst.The inner cell mass of the blastocyst develops into embryo.Embryonic stem cells(ES cells)areisolated from the
9、 inner cell massES Cell CultureDetermination The earliest changes that set a cell to a specialized stage without turning back at molecular level.Molecular changes that drives the process in the embryo is termed determination,the beginning of differentiation.During embryonic development,cells become
10、obviously different in structure and function as they differentiate.Differentiated Cells These cells produce the proteins that allow them to carry out their specialized roles in the organism.For example,only lens cells devote 80%of their capacity for protein synthesis to making just one type of prot
11、eins,crystallins.These form transparent fibers that allow the lens to transmit and focus light.Similarly,skeletal muscles cells have high concentrations of proteins specific to muscle tissues,such as muscle-specific version of the contractile protein myosin and the structural protein actin.They also
12、 have membrane receptor proteins that detect signals from nerve cells.PlacentaAllantoisYolk sacMothers bloodvesselsAmnioticcavityEmbryoChorionChorionicvilliFunctions of the chorion:1.Provide nutrients and O2 to the fetus2.Secrete hormones into the mother to help retain the fetus3.Repress the mothers
13、 immune response to prevent rejection of the fetus4.The placentas chorionic villi absorb food and oxygen from the mothers blood EctodermPattern FormationDifferentiation is carefully orchestrated:Proliferation Cell migration Interactions(Induction)Epithelial-mesenchymal transformations Epithelial fol
14、ding,movement,evagination,fusion Apoptosis ApoptosisLineage analysis of C.elegans highlights another outcome of cell signaling,programmed cell death or apoptosis.The timely suicide of cells occurs exactly 131 times in the course of C.eleganss normal development.At precisely the same points in develo
15、pment,signals trigger the activation of a cascade of“suicide”proteins in the cells destined to die.a.b.InhibitorCED-9Bcl-2CED-4Apaf1Caspase-8 or-9ApoptosisCED-3ApoptosisInhibitor:Activator:ApoptoticProtease:Caenorhabditis elegansMammalian CellOrganismInhibitionActivationIf it werent for apoptosis,yo
16、u may look a little different Apoptosis pathways in humans and other mammals are more complicated.Research on mammals have revealed a prominent role for mitochondria in apoptosis.Signals from apoptosis pathways or others somehow cause the outer mitochondrial membrane to leak,releasing proteins that
17、promote apoptosis.A cell must make a life-or-death“decision”by somehow integrating both the“death”and“life”(growth factor)signals that it receives.Apoptosis is essential to the development of animal morphogenesis(prevents webbing between fingers and toes).Model Organism(1)The Worm The nematode C.ele
18、gans normally lives in the soil but is easily grown in petri dishes.Only a millimeter long,it has a simple,transparent body with only a few cell types and grows from zygote to mature adult in three and a half days.Its genome has been sequenced.Because individuals are hermaphrodites,it is easy to det
19、ect recessive mutations.Self-fertilization of heterozygotes will produce some homozygous recessive offspring with mutant phenotypes.A further important feature is that every adult C.elegans have exactly 959 somatic cells.These arise from the zygote in virtually the same way for every individual.Stud
20、ying WormsC.elegans is a very useful model organism for investigating the roles of cell signaling and induction in development.The pathway from fertilized egg to adult nematode involves four larval stages(the larvae look much like smaller versions of the adult)during which the vulva develops.Six cel
21、ls present on the ventral surface of the second-stage larva gives the vulva.A single cell in the embryonic gonad,the anchor cell,initiates a cascade of signals that establishes the fate of the vulva precursor cells.Vulva development in the nematode illustrates several important developmental concept
22、s:In the developing embryo,sequential inductions drive the formation of organs.The effect of an inducer can depend on its concentration.Inducers produce their effects via signal-transduction pathways similar to those operating in adult cells.The induced cells response is often the activation(or inac
23、tivation)of genes which establishes the pattern of gene activity characteristic of a particular cell type.Genetics as a powerful approach for elucidating the mechanisms of development.A fate map traces the development of an embryo.Model Organism(2)The Fruit Fly The fruit fly Drosophila melanogaster
24、was first chosen as a model organism by geneticist T.H.Morgan and intensively studied by generations of geneticists.The fruit fly is small and easily grown in the laboratory.It has a generation time of only two weeks and produces many offspring.Embryos develop outside the mothers body.In addition,th
25、ere are vast amounts of information on its genes and other aspects of its biology.However,because first rounds of mitosis occurs without cytokinesis,parts of its development are superficially quite different from what is seen in other organisms.Sabotaging the Fruit FliesIn the 1940s,Edward B.Lewis d
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