Introduction to Genetic Analysis 621

Introduction to Genetic Analysis 621 - 44200_19_p611-642...

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present in the protein. Such studies also show that dif- ferent regions of the same protein have different amounts of polymorphism. For the esterase-5 protein, consisting of 545 amino acids, 7 percent of amino acid positions are polymorphic, but the last amino acids at the carboxyl terminus of the protein are totally invariant between individuals, probably because these amino acids are needed for the protein to function properly. Second, DNA sequence variation can also be studied in those base pairs that do not determine or change the protein sequence. Such base-pair variation can be found in DNA in 5 9 ±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. If that is true, then much of the sequence variation in cod- ing regions and in the amino acid sequences for which they code is beside the point. There is also variation in
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