present in the protein. Such studies also show that dif-ferent regions of the same protein have differentamounts of polymorphism. For the esterase-5 protein,consisting of 545 amino acids, 7 percent of amino acidpositions are polymorphic, but the last amino acids atthe carboxyl terminus of the protein are totally invariantbetween individuals, probably because these amino acidsare needed for the protein to function properly.Second, DNA sequence variation can also be studiedin those base pairs that do notdetermine or change theprotein sequence. Such base-pair variation can be foundin DNA in 59±anking sequences that may be regulatory.The importance of studying variation in regulatory se-quences cannot be overemphasized. It has been sug-gested that most of the evolution of shape, physiology,and behavior rests on changes in regulatory sequences. Ifthat is true, then much of the sequence variation in cod-ing regions and in the amino acid sequences for whichthey code is beside the point. There is also variation in
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