Lecture_7_phylogenetics

De substuons inserondeleons or genome rearrangements

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Unformatted text preview: different gene?c variants become dominant •  Any two species share a (possibly distant) common ancestor 15 •  •  •  •  •  Closer related organisms have more similar genomes Highly similar genes are homologous (have the same ancestor). A universal ancestor exists for all life forms. Molecular difference in homologous genes (or protein sequences) are posi?vely correlated with evolu?on ?me. Phylogene?c rela?on can be expressed by a evolu?onary tree . Phylogene?c Trees DNA is a Good Tool for Taxonomy DNA sequences have many advantages over classical types of taxonomic characters: Aardvark Bison Chimp Dog Elephant •  Leafs - current day species •  Nodes - hypothe?cal most recent common ancestors •  Edges length – ?me from one specia?on to the next –  Character states can be scored unambiguously –  Large numbers of characters can be scored for each individual –  Informa?on on both the extent and the nature of divergence between sequences is available (nucleo?de subs?tu?ons, inser?on/dele?ons, or genome rearrangements) 17 3 9/16/13 Sequences Reflect Rela?onships •  Aker working with sequences for a while, one develops an intui?ve understanding that for a given gene, closely related organisms have similar sequences and more distantly related organisms have more dissimilar sequences. •  These differences can...
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