BIO SCI 99 Problem Set #3 Key 1. In the experiment by Khorana, a synthetic mRNA having the repeating dinucleotide (AC) n , when translated using a bacterial extract, was found to direct the incorporation of the amino acids His and Thr. To determine which codon (ACA or CAC) coded for which amino acid, a synthetic mRNA having a repeating trinucleotide (AAC) n was then translated. This mRNA directed the incorporation Asn, Thr and Gln as a result of the three coding possibilities; AAC, ACA or CAA. The only codon found in both experiments was ACA and the only amino acid in both was Thr suggesting that ACA codes for Thr and by default, CAC codes for His. If synthetic mRNA having the trinucleotide repeats (ACC) n , (CCA) n , (CAC) n or (ACA) n were used in this analysis, would Khorana have been able to identify the correct codon/amino acid relationships? Demonstrate for each mRNA why or why not. If the RNA (ACC)n is used there would be three peptides formed; poly Thr (ACC), poly Pro
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