Molecular Evolutionary Analysis. Dan Graur. 1959. Q: We may ask the question where in the now living systems the greatest amount of information of their past history has survived and how it can be extracted? A: Best fit are the macromolecules which carry the genetic information.
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Molecular Evolutionary Analysis
Q: We may ask the question where in the now living systems the greatest amount of information of their past history has survived and how it can be extracted?
A: Best fit are the macromolecules which carry the genetic information.
“Searching for an objective reconstruction of the vanished past is surely the most challenging task in biology.”
“In one sense, everything in biology has already been ‘published’ in the form of DNA sequences of genomes.”
Life is monophyletic
Any two organisms share a common ancestor in their past
Some organisms have very recent ancestors.
Some have less recent ancestors…
…and less recent.
But, any two organisms share a common ancestor in their past
The differences between 1 and 2 are the result of changes on the lineage leading to descendant 1+those on the lineage leading to descendant 2.
Step 1:Sequence Alignment
Step 2: Translating number of differences into number of changes (steps).
1. the number of nucleotide substitutions per site between two non-coding sequences (K) according to Kimura’s two parameter model
2. the number of synonymous nucleotide substitution per synonymous site between two coding sequences (KS) according to Jukes and Cantor’s one parameter model
Example: the number of nonsynonymous nucleotide substitution per nonsynonymous site between two coding sequences (KA) according to Jukes and Cantor’s one parameter model
Ki = number of substitutions (or replacements) of type i per number of sites of type i per 2T
r = rate of substitution = number of
substitutions per site per year