deletions | additions       diff --git a/Building a 16S rDNA Phylogenetic Tree.md b/Building a 16S rDNA Phylogenetic Tree.md  index c43788a..170a9cd 100644  --- a/Building a 16S rDNA Phylogenetic Tree.md  +++ b/Building a 16S rDNA Phylogenetic Tree.md 
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With an unknown microbial species, the best way to identify it is to sequence one of its genes (most people  use the 16S rRNA gene) and ask what _it_ most looks like. With animal classification, the key features to examine are things like legs and wings and horns; with microbial  classification, the key features to examine are the nucleotides in different positions in a DNA sequence. Fortunately, we have computer programs to help us make  sense of the DNA sequence information. Our preferred approach to identifying a classifying  microbial species is to place the an  unknown sequence in the context of a phylogenetic tree of known sequences. Building a phylogenetic tree from a 16S rRNA sequence is fairly straightforward, but the interpretation of the tree can be  a bit of an art. Here, we attempt to guide you through both. However, some complicated cases will require consultation with an expert in the field of  phylogenetics or systematics.