An example of Molecular Evolution: cytochrome c

    Cytochrome c is an enzyme of the respiratory chain in the mitochondria of eukaryotes.  The sequences of cytochrome c from twenty species of animals, plants and fungi are presented in the figures below (they may be viewed in more detail by clicking on them--Adobe Acrobat Reader required).  The red columns indicate invariant sites--sites at which all species have the same amino acid.  Amino-acid identity at these evolutionarily conserved sites is crucial for proper functioning of the molecula.  Other sites show variability among species, indicating that evolutionary substitutions have occurred.
 

(From M. O. Dayhoff.  1969.  Computer analysis of protein evolution.  Scientific American 221: 87-95)

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