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Unformatted text preview: ino acid has changed more than
once. Since this multiple change would only appear to be
one substitution, it is necessary to compensate using the
! raw substitutions #
Corrected substitutions = - 100ln 1 "
in this case :
corrected sub' s = - 100ln 1 " 100 $
= - 100ln(0.67)
= 40 corrected substitutions
With fewer than 10 substitutions, the correction is not
For cytochrome c, one substitution occurs roughly
every 21 million years. Therefore humans and plants last
common ancestor lived about 850 million years ago. This
agrees roughly with the fossil record. Graph from The Structure
and Function of Proteins
Dickerson & Geis.
Corrected # of amino acid substitutions
Evolution 9 - 3 Molecular phylogeny & criminal justice
• 1994: Dr. Richard Schmidt accused of injecting his ex-girlfriend (the Victim) with
HIV (AIDS virus) from one of his patients.
HIV evolves very rapidly, even leading to multiple different sequences in the same
Police collected HIV samples from victim (V), Dr. Schmidt’s patient (P), and many
local HIV+ individuals from the community who were unrelated to the case (LA)
They then used computer tools to construct the following phylogeny. From: “Molecular evidence of HIV-1 transmission in a criminal case” by Michael L.
Metzker, David P. Mindell, Xiao-Mei Liu, Roger G. Ptak, Richard A. Gibbs, and David
M. Hillis. Proceedings of the National Academy of Sciences 99:22 14292-14297 (2002). Evolution 9 - 4...
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