BIOL 2P05 Lecture Notes - Lecture 10: Maximum Likelihood Estimation, Ingroups And Outgroups, Sequence Homology
7 Mar 2016
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A monophyletic group is a taxon which forms a clade, meaning that it consists of an ancestral species and all its descendants. Natural monophyletic group / unnatural paraphyletic group. Look if it contains a common ancestor and all the descendants = monophyletic. A polyphyletic taxon is defined as one that does not include the common ancestor of all members of the taxon. Doesn"t include all of the common ancestor and the include groups it does not belong. Homology is the existence of shared ancestry between a pair of structures, or genes, in different species. Pair of limbs, from certain animals and birds. Only homologous genes can be used in a phylogeny** Homology between protein or dna sequences is defined as always in terms of shared ancestry but new nomenclature. Two segments of dna can have shared ancestry because if either a speciation events (ortholog) or a duplication even (paralogs) Conservations + function + sequence you have paralogous genes.
