deletions | additions       diff --git a/Building a 16S rDNA Phylogenetic Tree.md b/Building a 16S rDNA Phylogenetic Tree.md  index fe4cf05..1ce176f 100644  --- a/Building a 16S rDNA Phylogenetic Tree.md  +++ b/Building a 16S rDNA Phylogenetic Tree.md 
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wanted to identify (or classify) it, you might look at it's morphology and ask what it most _looks_ like. If it has six legs, you might guess it's some kind of  insect. If it has hard outer wings folded over its back, you might guess that it's some kind of beetle. If it also had antler-style horns on its head, you might  guess that it's some kind of stag beetle. If you don't have enough information available to guess what kind of stag beetle you have, then you have reached the  limit of *taxonomic resolution* for your creature. 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 microbial species is to place the unknown sequence in the context of a