Question

You decide you are going to decipher codons of an unknown mRNA transcript. In a test tube you mix the unknown mRNA template, all of the tRNAs for all 20 amino acids, all 20 amino acids and a large concentration of ribosomal subunits. You end up producing 3 distinct polypeptides of poly-valine, poly-arginine and poly-serine. What is the sequence of the unknown mRNA?

 A) 5'-AGCAGCAGCAGCAGC-3' B) 3'-AGCAGCAGCAGCAGC-5’ C) 3'-UGCUGCUGCUGCUGC-5' D) 5'-UCAUCAUCAUCAUCA-3’ E) None of the above

Answer 1

the unknown mRNA sequence is none of of the above

because to make valine is coded by sequence GUU,GUA,GUC and GUG, same way Arginine codede by sequence CGU,CGA,CGC and CGC, and serine is coded by AGC and AGU. in given option C sequence can make only two poly amino acid sequence i.e. poly valine and ploy arginine but not poly serine so that answer is none of the above sequence.