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Building and visualizing phylogeny Henrik Lantz Dept. of Medical Biochemistry and Microbiology, BMC, Uppsala University
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Me PhD in Plant Systematics, post doc in Fungal Systematics Now bioinformatician working with genomic and transcriptomic data, mostly annotation of genomes
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You How many of you have experience with inferring phylogenies? How many of you have experience with working with sequence data in the computer?
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This lecture Basic facts about phylogenies and nomenclature used How to infer a phylogeny from sequence data How to visualize phylogenies
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What is phylogeny? Evolutionary relationship of organisms or genes – anything related by descent Often visualized as a phylogenetic tree
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From individual to phylogeny
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Zoooooming out…
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Overview
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Organism based phylogeny
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Gene families
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A simple phylogeny Branch Node Root Time
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ABCD Root CDAB Clades
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ABCD Root CDAB Sister groups
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ABCDEFGH Sister-group relationships
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MouseRabbitChimp Human BirdsKangarooHorseDog
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ABCDEFGH Monophyletic Paraphyletic
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Support values
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Branch lengths
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Phylogeny 1-2-3 1. Sequence data, nucleotides or amino acids, in FASTA-format 2. Align the sequences 3. Run the alignment in the phylogeny program 4. Visualize the results in a tree viewer Phylogeny.fr does all of this!
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Expasy
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Phylogeny.fr
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1. Fasta-format >CO1_species1 ACGTGTCCGA... >CO1_species2 TCCGATGAAC... >CO1_species3 GTGTCCGATC... Etc.
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2. Alignment From: >CO1_species1 ACGTGTCCGA >CO1_species2 TCCGATGAAC >CO1_species3 GTGTCCGATC To: >CO1_species1 ACGTGTCCGA----- >CO1_species2 -----TCCGATGAAC >CO1_species3 --GTGTCCGATC---
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2. Alignment >CO1_species1 ACGTGTCCGA----- >CO1_species2 -----TCCGATGAAC >CO1_species3 --GTGTCCGATC--- >CO1_species4 ACGTGACCGATC--- >CO1_species5 -CGTGACCGATCAAC >CO1_species6 ACGTGTCCGATGAAC
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Homology and orthology Homology - traits shared due to common ancestry, e.g., fingered forelimbs in birds and mammals Analogy - traits of similar function, but not due to shared ancestry, e.g., wings in birds and insects Orthology - Sequences were split due to speciation events Paralogy - Sequences were split due to duplication events
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Outgroup Should be something outside of the study group. Used to orient the tree. If you can, pick several taxa as outgroup Most phylogenetic programs pick the upper-most sequence in your input-file as the outgroup unless you tell the program otherwise
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3. Build the phylogeny - Phylogenetic methods UPGMA Neighbor joining Parsimony Likelihood methods - Maximum Likelihood - Bayesian Methods Do not use! Not recommended Outdated Use one of these Phyml, Raxml MrBayes
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Substitution models Jukes-Cantor - Transitions between all nucleotides are the same Kimura - Different rates for transitions and transversions (Purine AG, Pyrimidine CT) GTR - Different rates for all transitions. Used by Phylogeny-fr Amino acid models become much more complex as there are 20 states rather than 4
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4. Visualization
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