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UCSD BILD 1 - Development

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When%glucose%is%present%A) cyclic'AMP'is'high,'the'catabolite'ac3vator'protein'(CAP)'binds'to'the'ac3vator'binding'site,'and'transcrip3on'of'lactose'operon''is'turned'on'B)'cyclic'AMP'is'low,'CAP'binds'to'the'site'ac3vator'binding'site,'and'transcrip3on'of'lactose'operon'is'turned'on'C)'cyclic'AMP'is'high,'CAP'does'not' bin d'to'the'ac3vator'binding'site,'and'transcrip3on'of'lactose'is'turned'on'D)'cyclic'AMP'is'low,'CAP'does'not'bind'to'the'ac3vator'binding'site,'and'transcrip3on'is'turned'off'Combina4on%of%posi4ve%and%nega4ve%regula4on%ensures%that%lactose%operon%will%be%transcribed%only%when%glucose%levels%are%low%and%lactose%levels%are%high%%Specifics of eukaryotic transcription 1. Three types of RNA Polymerases are responsible for transcribing different genes 2. General Transcription factors are required to assist RNA Polymerase binding to promoter 3. Specific transcription factors determine if a gene is on or off in any particular cellThree types of RNA Polymerases are responsible for transcribing different genes: 1. RNA Pol I - most rRNA genes 2. RNA Pol II - all protein-coding genes, some small RNA’s (snRNA’s, for example) 3. RNA Pol III - tRNA, 5S rRNAIn order to initiate transcription, eukaryotic RNA Polymerase requires assistance of general transcription factors Transcrip3on'ini3a3on'complex'Fig. 18-9-1 Enhancer TATA box Promoter Activators DNA Gene Distal control elementFig. 18-9-2 Enhancer TATA box Promoter Activators DNA Gene Distal control element Group of mediator proteins DNA-bending protein General transcription factorsFig. 18-9-3 Enhancer TATA box Promoter Activators DNA Gene Distal control element Group of mediator proteins DNA-bending protein General transcription factors RNA polymerase II RNA polymerase II Transcription initiation complex RNA synthesisFig. 18-10 Control elements Enhancer Available activators Albumin gene (b) Lens cell Crystallin gene expressed Available activators LENS CELL NUCLEUS LIVER CELL NUCLEUS Crystallin gene Promoter (a) Liver cell Crystallin gene not expressed Albumin gene expressed Albumin gene not expressedClicker question This binds to a site in the DNA far from the promoter to stimulate transcription: A) enhancer B) promoter C) activator D) repressor E) General transcription factorMultiple levels of gene regulation in eukaryotes The most important level of gene expression regulation is the regulation of transcriptionIndependent study Mechanisms of post-transcriptional regulation: Ch. 18 pp. 362-364 Two helpful animations: Transcription Complex and Enhancers Control of Gene Expression in Eukaryotes http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter18/animations.html#Regulation of genes in DevelopmentFig.47-7 The biggest question in developmental biology: how do you get from a single cell to a functional organism? Early embryonic development of a human Fertilized egg Four-cell stage Two-cell stage BlastocystMutations in fly Hox genes indicated that a single gene can control development of entire regions of the body Ed Lewis!Bithorax mutants have!two thoracic (winged) !segments, instead of one!Eye Antenna Leg Wild type Mutant A mutation in one of the master control genes, Antennapedia, produces a fly that has legs instead of antennaeEight Hox genes in the fruit fly genome!a family of genes, each with a homeobox sequence!Homeobox sequences!The protein products of Hox genes are transcription factors - proteins that turn other genes on or offHox gene activity patterns in fly embryo!Head!Tail!Hox genes expressed and act very early in embryonic developmentMammal Hox genes and fly Hox genes are homologous—inherited from our common ancestorLimb defects from mutation of human Hox genes heterozygotes!Hox master control genes - what do they do? Hox genes help lay out the basic body forms of many animals, including humans, flies, and worms. They set up the head-to-tail organization. You can think of them as directing instructions as an embryo develops: “Put the head here! Legs go over there!”A sophisticated worm that existed 500 million years ago was the ancestor to all modern animals!The notion that all animals (including me) have a common ancestor is: A. Highly probable B. Somewhat probable C. Don’t know what to think about it D. Somewhat improbable E. Can’t possibly be trueCell Differentiation In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type.Which cell types are these? Red blood cell White blood cell Platelet Heart muscle fibersIn most cases, differentiation is controlled at the level of A) replication of the DNA. B) nucleosome formation. C) transcription. D) translation. E) post-translational activation of the proteins.• Expression of genes for tissue-specific proteins (cell determination ) • Tissue-specific proteins enable differentiated cells to carry out their specific tasks and obtain their unique shapes Stages of cell differentiationFig.21-10_1 Nucleus Embryonic precursor cell DNA OFF OFF Master control gene myoD Other muscle-specific genes Example: determination and differentiation of a muscle cell This cell can also become: A cartilage cell a fat cellFig.21-10_2 Nucleus Embryonic precursor cell DNA OFF OFF Master control gene myoD Other muscle-specific genes mRNA OFF Determination Myoblast (determined) MyoD protein (transcription factor)Fig.21-10_3 Nucleus Embryonic precursor cell DNA OFF OFF Master control gene myoD Other muscle-specific genes mRNA OFF Determination Myoblast (determined) MyoD protein (transcription factor) Differentiation Muscle cell (fully differentiated) mRNA MyoD mRNA mRNA mRNA Another transcription factor Myosin, other muscle proteins, and cell-cycle blocking proteinsA cell that remains entirely flexible in its developmental possibilities is said to be A) differentiated. B) determined. C) totipotent. D) genomically equivalent. E) epigenetic.The last word from Darwin!There is grandeur in this view of life . . !that from so simple a beginning, endless forms most beautiful and most wonderful have been, and are being, evolved.!Summary: important points A. Major stages of embryonic development are: fertilization, cleavage, gastrulation, organogenesis B. At early stages of development, all vertebrate embryos are very similar C. Cell determination precedes differentiation and involves expression of genes for tissue-specific


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UCSD BILD 1 - Development

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