BS9906PS3 - n , (CCA) n , (CAC) n or (ACA) n were used in...

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BIO SCI 99 Problem Set #3 Name________________________________Student Number_______________________________ 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)
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Unformatted text preview: 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. 2. Which amino acids require only one tRNA molecule in order to recognize all of their codons? Which amino acids require at least three tRNA molecules in order to recognize all of their codons? 3. Can the base sequence of an mRNA be predicted from the amino acid sequence? Why or why not? 4. There are 20 different amino-acyl tRNA synthetases, one per amino acid. Some synthetases need to recognize more than one cognate tRNA and therefore more than one anti-codon. How is this possible?...
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