Introduction to Genetic Analysis 11

Introduction to - 10 Chapter 1 • Genetics and the Organism carry out genetic analysis because mutations that affect some specific biological

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Unformatted text preview: 10 Chapter 1 • Genetics and the Organism carry out genetic analysis because mutations that affect some specific biological function under study identify the various genes that interact in that function. enzymes—tyrosinase. The enzyme tyrosinase catalyzes the last step of the pathway, the conversion of tyrosine into melanin. To perform this task, tyrosinase binds to its sub- strate, a molecule of tyrosine, and facilitates the molecu- lar changes necessary to produce the pigment melanin. There is a specific “lock-and-key” fit between tyrosine and the active site of the enzyme. The active site is a pocket formed by several crucial amino acids in the polypeptide. If the DNA of the tyrosinase-encoding gene changes in such a way that one of these crucial amino acids is replaced by another amino acid or is lost, then there are several possible consequences. First, the en- zyme might still be able to perform its functions but in a less efficient manner. Such a change may have only a small effect at the phenotypic level, so small as to be dif- ficult to observe, but it might lead to a reduction in the amount of melanin formed and, consequently, a lighter skin coloration. Note that the protein is still present more or less intact, but its ability to convert tyrosine into melanin has been compromised. Second, the en- zyme might be incapable of any function, in which case the mutational event in the DNA of the gene would...
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

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