Role of gene duplication in the evolution of complex physiological mechanisms : an assessment based on protein sequence data : (gene duplication, protein sequences, evolutionary trees, serine proteases, immunoglobulins, evolution of muscle types)
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Genetic duplication has played a major role in the evolution of physiological complexity by creating originally redundant genes that evolved to produce related proteins in the organism. The related chains of certain polymeric molecules permit a range of similar activities while maintaining specificity. Related proteases form simple and complex cascade mechanisms that are poised for a controlled burst of activity, such as that seen in blood coagulation. Related genes arranged tandemly on the same chromosome may evolve to produce proteins that appear serially during development, as do the epsilon, gamma, and delta and beta chains of hemoglobin. Duplication can also produce an elongated gene that codes for a protein with multiple functional sites. Such proteins are important for the development of complex physiological functions such as muscle contraction. Polymeric structure, multiple genes, and internal duplication combine to give the immunoglobulins extraordinary functional diversity. Duplication of genetic material provides the raw material for the specialization of cell and tissue types.