How might similarities and differences in genetic codes be used to determine how closely related different species are?

Question

anonymous · Answer

There is an algorithm called BLAST (basic local alignment search tool) that compares and contrasts nucleotide sequences. It attempts to find matching segments of genes and a heuristically assigned "score" to the match, which tells us how sequentially similar the genes are.

Once we have an objective method of noting how similar genes are, it's pretty much up to our imagination (and further research). Maybe there's shared ancestry? Maybe both species transcribe this amino acid? So on and so forth.

anonymous · Answer

their are many other tools for sequence comparionson.
They are used depending on puropose. 
I will suggest to use Phylip