MICR 2123 Lecture Notes - Lecture 12: Carl Woese, Molecular Phylogenetics, Silent Mutation
17 Oct 2016
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Molecular phylogeny or genetic relatedness generates a series of branching groups of related organisms called clades: a group of species that share a common ancestor. How does divergence occur between different clades over time: random mutations: as the chromosome replicates, errors result in mutations. Neutral mutations have no effect no gene function (e. g. silent mutation: natural selection: in an environment, some genes are under selection pressure, reductive (degenerative) evolution: loss or mutation of dna encoding unselected traits. The most widely used is the gene encoding the small subunit rrna (ssu rrna: 16s rrna (bacteria) or 18s rrna (eukaryotes) All phylogenetic trees depend on complex mathematical analysis to determine the most probable tree. Estimates the relative amounts of evolutionary divergence between the sequences. Carl woese first used ssu rrna phylogeny to reveal the existence of a third kind of life: the archaea. The three fundamental groups of life-forms bacteria, archaea, and eukarya are termed domains.
