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MCB 317 Genetics and Genomics Topic 11, pt 3 Genomics
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Genomics Summary A.Microarrays: expression profiling and other uses B.Global Gene Knockouts C.Global protein localization in yeast D.Global complex identification in yeast E.Global two-hybrid analysis in yeast and other organisms F.RNAi G.Transgenics, gene “knock-outs” (genetics not genomics) H.Next Generation Sequencing Genome sequencing ChIP seq RNA seq I.Comparative Genomics, Evolution and Human History
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Ab Protein Txn Profile Gene Orthologs and Paralogs Mutant Gene Biochemistry Genetics Mutant Organism A C F Subunits of Protein Complex B, G D E Protein Profile/ Localization Genomics: High-throughput genetics Genomics B, G H Gene/Protein DNA binding sites I
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RNA Seq mRNA or total RNA DNA Sequence “Transcriptome”
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ChIP Seq DNA pulled down by ChIP Sequence All chromosomal sites bound by YFP
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Genomics Summary A.Microarrays: expression profiling, RNA seq B.Global Gene Knockouts C.Global protein localization in yeast D.Global complex identification in yeast E.Global two-hybrid analysis in yeast and other organisms F.RNAi G.Transgenics, gene “knock-outs” (genetics not genomics) H.Human Genome Project, Next Generation Sequencing, and Comparative Genomics I.ChIP for specific binding site, ChIP seq for all binding sites throughout the genome
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Science 296: 1661-1671 Human-Mouse comparison
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Alb 4-18 MouseHuman Genomic Synteny Map
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Mouse Chr. 16- Human Comparison Science 296: 1661-1671 31 May 2002 Synteny
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Human-Mouse Synteny Mouse chr. 16 =Human chr. 3, 8, 12, 16, 21, 22 Mouse chr.16 - Human Gene comparison –731 predicted genes –509 = Orthologs of human in syntenic regions –44 = paralogs –164 = Homologs elsewhere in human genome –14 = No human counterpart (2% unique genes) Look at Human regions of synteny –2.9% genes unique to humans
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Thinking about Human-Mouse Synteny 85,000,000 years of divergence 300 “flips” 85,000,000/300 = 283,333 years per flip
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Human-Puffer Fish Synteny 400 million years of divergence Syntenic blocks = 10 Kb in size
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Generation of Protein Diversity by Alternate Splicing Neurexins are (one type of) neuronal adhesion proteins. They mediate connections between neurons 3 Neurexin Genes -> 2,000 splice variants Human Brain 100 x 10 9 Neurons Each Neuron makes ~1,000 connections Total # of Connections = 100 x 10 12
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Alternate Splicing and Domain Architecture
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Major Forces in Evolution of Higher Organisms Gene duplication and divergence -> gene families Alternate Splicing and Domain Architecture Chemical modification ala “histone code” -> lots of chemical modifications to lots of proteins, not limited to histones Not a huge increase in number of genes in humans but each gene -> variety of related proteins
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Human Evolution from Primates
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Darwin and Wallace Gave us Natural Selection (Speciation); Mendel gave us a “Mechanism” Species 1 Sp2Sp3 Mutation(s) and Natural Selection
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Darwin and Wallace: One Species Gives Rise to Another Species 1 Sp2Sp3 Sp4Sp5Sp6Sp7Sp8 Sp9 Sp14 Sp4 Sp10 Sp11Sp12 Sp13 Sp7 Sp16 Sp17 Sp12Sp13 Darwin also realized the reverse was true…
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Darwin Invented Genealogy! Darwin’s Doctrine of Common Descent: “(P)robably all of the organic beings which have ever lived on this earth have descended from some one primordial form…” Darwin predicted a “…time when we shall have very fairly true genealogical trees of each great kingdom of nature.” Typical Textbook: “All organisms on earth today are the descendants of a single kind of unicellular organism that lived almost 4 billion years ago.”
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Estimate Time from Common Ancestor Sp14 Sp4Sp11Sp12 Sp13 Sp7 Sp16 Sp17 Time = Mutations/(Mutation Rate)
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Phylogenetic Tree
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Human-Chimp Divergence ~ 5,500,000 years ago
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Within a Population (e.g. Humans) Ind1 Ind2Ind3Ind4 Ind5 Ind6 Ind 7 Ind8 Time = Mutations/(Mutation Rate)
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Within a Population (e.g. Humans) Ind1 Ind2Ind3Ind4 Ind5 Ind6 Ind 7 Ind8 Look at Mitochondrial Sequences: Maternal Lineage
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Mitochondrial Eve lived 100,000 - 200,000 years ago 10,000-50,000 human population
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Look at Y-chromosome: Paternal Lineage Ind1 Ind2Ind3Ind4 Ind5 Ind6 Ind 7 Ind8 Y-chromosome Adam = 95,000 years ago in Sub-saharan Africa ~2,000 men left Africa 67,000 years ago
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Hartl6 16.5
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5,500,000 years ago = divergence of our ancestors from Chimpanzees 600,000 years ago Hominids in Africa 200,000- 300,000 + years ago groups of hominids began leaving Africa and founded populations elsewhere (e.g. Neandertals) 200,000 years ago ~ Homo sapien morphology (look like us) 100,000+ years ago “mitochondiral Eve” was part of a founder population of 10,000 - 50,000 people 95,000 years ago -> Y-chromosome “Adam” lived in Sub-saharan Africa 30,000-50,000 years ago the population of humans that left Africa inter- bred with Neanderthals in the Middle East -> People of European and Asian descent have some Neanderthal alleles -> skin phenotypes: skin color and keratin intermediate filaments Model from a Collection of Recent Data
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Evolution of Keratins Keratin family seems to have arisen at the time that animals with soft exteriors appeared. Animals that lack an exoskeleton.
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Roles of Intermediate Filaments Distribute tensile forces across cells in tissues Integrate cells into tissues
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Intermediate Filaments and Human History
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Neanderthal-Human divergence ~600,000 years ago Modern Humans migrated out of Africa ~100,000 years ago Humans interbred with Neanderthals ~50,000-60,000 years ago in Middle East Modern Humans migrated to Europe and Northern Asia ~40,000-45,000 years ago Neanderthals died out ~30,000 years ago
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Sequencing Neanderthal Genomes and Comparing DNA with Modern Humans The complete genome sequence of a Neanderthal from the Altai Mountains Nature 2 Jan 2014; 505:43 Resurrecting Surviving Neandertal Lineages from Modern Human Genomes Science 28 February 2014; 343:1017
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Human DNA Derived from Neanderthals in non-Africans 1.BNC2 a zinc finger protein associated with skin pigmentation 2.POUF2F3 a transcription factor expressed in epidermis that mediates keratinocyte proliferation and development 3.A cluster of keratin genes
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Common Chimps (Pan troglodytes), Bonobos (Pan paniscus, or pygmy chimps), the Congo River and 1-2 million years of evolution… …and 6.5 million years of evolutionary divergence from Homo sapiens: comparative genomics of primates
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Svante Paabo: Human FOXP2 allele ~200,000 to 50,000 yrs ago -> speech and language. Could the development of advanced speech and language be the result of the human FOXP2 allele? The human WT allele differs in 2 positions from the WT chimp allele. Originally speculated to have occurred after our split from Neanderthals; however, recent data indicates that the FOX2P language allele that humans have but that chimps lack was also found in Neanderthal DNA FOX2P was subject to a “genetic sweep”
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Micro-encephalin contributes to brain size Human allele arose ~ 37,000 years ago which corresponds to the time that art, music and advanced tool-making emerged in the human population; however note that the date of 37,000 years ago comes with error bars of 23,000 years [but how does this fit with the idea that Y Adam and Mito Eve existed 100,000 years ago?
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ASPM a gene also involved in brain size/development. Human specific allele is thought to have arisen only 5,800 years ago. Newspaper version: “This is approximately time time when language, agriculture and cities began to appear.” Gene v. allele Correlation v. actual evidence 5,800 yrs, v. 500 -14,000 yrs Statements/observations like this are in the early stages of understanding and are controversial… if not down-right wrong! Human Specific ASPM Allele
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Comments on Genetic Diversity and Evolution
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35 Generations
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Mitochondrial Eve and Y-chromosome Adam ~ 100,000 years ago Assume 15 yrs/generation 100,000/15 = ~ 6,700 generations of modern Homo sapiens If 20 yrs/generation 100,000/20 = ~ 5,000 generations of modern Homo sapiens
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Comments on Life on Our Planet
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Timeline of the Universe and Earth 0Time (Billions of Years) 14.510 20 Estimated Lifespan of our Sun What type of atoms were created in the big bang?
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Timeline of the Universe and Earth 0Time (Billions of Years) 14.510 20 Estimated Lifespan of our Sun Massive stars created the “heavy” elements ( > H) and exploded spreading those elements, which formed new stars and planets…. including us…
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The Birth of “Our” “Heavy” Atoms
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Some Major Events in Evolution and Biological History From birth of heavy atoms To formation of molecular O 2 To mitochondria and nuclei To dinosaurs Ice age -> humans…. Human chimp divergence
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