Molecular Evolution

Protein Evolution

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Proteins are the essential building blocks of living cells; indeed, life can be viewed as resulting substantially from the chemical activity of proteins. Because of their importance, it is hardly surprising that ancestors for most proteins observed today were already present at the time of the 'last common ancestor', a primordial organism from which all life on earth is descended. Proteins are strings of amino acids transcribed from genes, and they typically fold into a particular shape to perform some function in a living system. Proteins evolve when one amino acid is substituted for another.

Proteins are strings of amino acids transcribed from genes, and they typically fold into a particular shape to perform some function in a living system. Proteins evolve when one amino acid is substituted for another. Amino acid substitutions occur frequently as species evolve from a common ancestor. In 1965 Emil Zuckerkandl and Linus Pauling observed that the rate of change in the amino acid sequence of hemoglobin was linear in time across species. This led to the idea of a molecular clock, or constant underlying rate of change that characterizes the evolution of a protein.