534 Chapter 16 • Dissection of Gene Function How does the introduction of double-stranded RNA inactivate the homologous gene? The mechanism of ac-tion of RNAi has been worked out in C. elegans (Figure 16-19). The introduced double-stranded RNA is chopped into segments 22 nucleotides long by a molecular com-plex called dicer . The pieces, called interfering RNAs , are then bound to a complex called the RISC (RNA-induced silencing complex) . An RNA component of the complex, called the guide RNA, helps the complex ±nd mRNAs complementary to the interfering RNAs. After binding to the target mRNA, the complex then degrades it. With translation brought to a halt by the absence of mRNAs, the organism expresses the mutant phenotype. CHEMIGENOMICS Another stage in the information-transfer process that can be targeted for phenocopying is the protein itself. A genomic-scale technique has been developed, which goes by the names chemigenomics or chemical genetics. This technique is based on reducing
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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.