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Molecular Clocks: Proteins that Evolve at Different Rates

The basic mutation rate is probably similar for all genes, but natural selection filters out mutations that adversely affect the functioning of the protein each gene makes. The structure of some proteins is rigidly defined by the function they perform -- any mutation that causes even a small change in the molecular structure will impair the protein's function. These proteins accumulate very few mutations and may be identical in many species, which means they have limited use in working out how closely different species are related. Other proteins can tolerate a large amount of change and still carry out their function. Such proteins accumulate many mutations, and they can be used to help work out the evolutionary relationships between even closely related species.

Credits: The Human Evolution Coloring Book, Second Edition, by Adrienne Zihlman, produced by Coloring Concepts Inc. and published by HarperCollins, New York

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Evolution of Diversity

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