Central Dogma and Gene Expression: Replication, Transcription, and Translation in Genetics, Study notes of School management&administration

Download Central Dogma and Gene Expression: Replication, Transcription, and Translation in Genetics and more Study notes School management&administration in PDF only on Docsity! DNA: The Central Dogma & Gene Expression Lecture 5 Genetics & Society Honor 3215, Fall 2008 Bryan Benham Outline •! Review –!What is the secret of life? –!What is a gene? •! The Central Dogma •! Gene Expression 2 Feb. 28, 1953: Two guys walk into a pub and declare they have the answer to the secret of life. 3 Secret of Life? •! Complementarity is the secret of life –! A-T and G-C –! Structure of DNA •! Needed for replication –! Copies: fast and accurate •! Replication is at the heart of all genetic functions –! DNA: instructions (blueprints) for biological processes –! Instructions need to be replicated for each process 4 How does this happen? Cells •! ~50-100 million million •! ~200 different types •! Each makes what it needs to survive and do its job: –! grow, multiple, communicate and cooperate with other cells as well as perform its particular function: e.g., carry oxygen and nutrients, flex/ contract, send messages, etc. •! Process and produce various materials –! Water (66%), proteins*, carbohydrates, fats, minerals 5 ? http://giant-panda.com/ 6 genes http://giant-panda.com/ 7 What is a gene? http://cmgm.stanford.edu/biochem201/Slides/Chromatin%20Structure/01%20Human%20Chromosome.JPG A gene is a section of DNA that makes a protein (usually several 10,000’s of base pairs long) 8 A gene is a section of DNA chromosome gene 9 Proteins do things Proteins •! Organic compounds made of chains of amino acids –! Only 20 different amino acids •! Proteins do things: –! E.g., catalysts (enzymes), structure and function (cytoskeleton), cell signaling and communication, metabolism of nutrients, etc. •! ~ 300,000 – 400,000 proteins in humans 10 How do genes make proteins? 11 The Central Dogma 12 RNA is copied from 1 DNA strand Transcription A G C T A G C A C T A C T G A A G T G C G C C T C G A T C G T G A T G A C T T C A C G C G G A G C T A G C A C T A C T G A A G T G C G C C T C G A T C G T G A T G A C T T C A C G C G G DNA A G C U A G C A C U A C U G A A G U G C G C C RNA (Complementarity again) 25 RNA is copied from 1 DNA strand Transcription A G C T A G C A C T A C T G A A G T G C G C C T C G A T C G T G A T G A C T T C A C G C G G A G C T A G C A C T A C T G A A G T G C G C C T C G A T C G T G A T G A C T T C A C G C G G DNA A G C U A G C A C U A C U G A A G U G C G C C RNA (mRNA- messenger) 26 RNA uses U in place of T RNA uses 4 base pairs, but instead of Thymine (T) it uses Uracil (U) Because DNA uses T, not U, the cell automatically assumes that U is the result of a C gone bad and removes all U bases from DNA. C U T Video: Transcription 28 Central Dogma DNA RNA Protein Replication Transcription Translation 29 Video: Translation 30 Protein is the final product of the information mRNA Protein Translation 31 Translation •! Messenger RNA (mRNA) •! Ribosome •! Codons •! Transfer RNA •! Amino Acids •! Proteins 32 Proteins are made of 20 different amino acids (you don’t have to know these diagrams) 33 Amino acids can be linked together 34 Proteins are long chains of amino acids Protein (a real protein would have hundreds of amino acids) 35 Proteins are long chains of amino acids Hemoglobin Protein chains fold into complex shapes that depend on the sequence of amino acids Protein 36 An (transfer) RNA adapter is used to convert RNA to Protein U A C tRNA Amino Acid 37 tRNa is made similarly in transcription Complementarity is used to convert the information in RNA into protein mRNA U C U A U C G U G A U A C C U U C A C G C Amino Acids tRNA A G A U A G C A C U A U G G A A G U G C G U G A 38 Complementarity is used to convert the information in RNA into protein U A C C U U U C C U C G A U U G A A C G C Protein mRNA A G A U A G C A C U A U G G A A G U G C G U G A 39 AUG is the translation start UAA UAG or UGA are stop U A C C U U U C C U C G A U U G A A C G C Protein mRNA A G A U A G C A C U A U G G A A G U G C G U G A START STOP 40 Codons 41 Video: Translation 42 Promoters and Transcription Factors •! Promoters are parts of a gene that identify that gene and determine when, where and how much of its product gets produced. •! Transcription Factors are proteins which interact with DNA (e.g., attach to beginning of gene) to control transcription. 55 Not all of the DNA gets copied into RNA DNA A gene is a piece of DNA that makes a protein RNA 56 Not all of the DNA gets copied into RNA DNA RNA •!Some of the DNA encodes when, where and how much of the RNA to make. This is called the promoter. promoter A gene is a piece of DNA that makes a protein 57 Transcription factors control gene expression DNA RNA promoter Transcription factor 58 Transcription factors control gene expression DNA promoter Transcription factor 59 Question Where do transcription factors come from? 60 Junk DNA? •! “Junk” DNA refers to the non-coding regions of DNA, but research shows that junk DNA ain’t so much junk. •! It appears that the non-coding regions regulate some gene expression. 61 Epigenetics •! Another way that gene expression is controlled is by limiting physical access to that gene. •! Methylation: attaching a methyl group to DNA, at the “C”, which effectively blocks transcription. •! Histones: DNA is packaged in loops around ball-like structures, called histones. In regions of DNA that are tightly packaged, those genes are not accessible for transcription. Those regions that are looser are accesible. •! In both cases, the mechanism for transcription (RNA polymerase, etc.) can not reach the genes. 62 63 •! Lifestyle and environment may effect one’s epigenetic code. •! Also, may be inherited FYI: Nova Science Now video: http://www.pbs.org/wgbh/nova/ sciencenow/3411/02.html 64 Environment •! Sun •! Smoking •! Exercise •! Food •! Atmosphere •! Etc. 65 Environment “The gene may not be central to the phenotype at all, or at last It shares the spotlight with other influences. Environmental, tissue and cytoplasmic factors clearly dominate the phenotypic expression processes, which may, in turn, be affected by a variety of unpredictable protein-interaction events.” – Paul Sliverman 66 Genotype does not equal phenotype Genes provide possibility or propensity, but do not independently determine product or expression. 67 The exact types and amounts of protein made by our DNA make us what we are. http://giant -panda.com/ DNA RNA Protein 68 Genes in some well known organisms <10 !m 12 M base pairs 6,300 genes ~1 mm 97 M base pairs 19,100 genes http://www.ornl.gov/sci/techresources/Human_Genome/faq/compgen.shtml#genomesize http://elegans.swmed.edu/ http://www.genomenewsnetwork.org /articles/12_03/yeast_screen.shtml 69 Genes in some well known organisms ~1 cm 180 M base pairs 13,600 genes ~10 cm 125 M base pairs 25,500 genes http://www.ornl.gov/sci/techresources/Human_Genome/faq/compgen.shtml#genomesize http://www.rhone-alpes-genopole.com/index.php?pageID=52&tabNum=2 http://www.cofc.edu/~bernardoj/Genetics%20Lab/212Lhome.htm 70 Genes in some well known organisms 2,500 M base pairs ~30,00 genes 2,900 M (~3 billion) base pairs ~30,000 genes http://www.ornl.gov/sci/techresources/Human_Genome/faq/compgen.shtml#genomesize http://www.bcgsc.ca/gc/mouse/ http://www.thatsweird.net/picture32.shtml 71 The exact types and amounts of protein made by our DNA make us what we are. http://giant -panda.com/ DNA RNA Protein 72