Question

The genetic code was elucidated through the use of polyribonucleotides synthesized either enzymatically or chemically in the laboratory. Given what we now know about the genetic code, how would you make a polyribonucleotide that could serve as an mRNA coding predominantly for may Phe residues and a small number of Leu and Ser residues? What other amino acid(s) would be encoded by this polyribonucleotide, but in smaller amounts?

Answer 1

Recall: DNA---Transcription----> m-RNA---------Translation------->proteins

To make polyribonucleiotide that serves as mRNA. It should have to start with start codon AUG which will code for amino acid Met. (Note: ribonucleotide will have U instead of T as base)

Phe amino acid residues use UUU and UUC codons.

Leu amino acid use UUA , UUG, CUU, CUC, CUA, CUG codons.

Ser amino acid uses UCU, UCC, UCA,and UCG codons.

As seen from this information, we will need polyribonucleotide with majority of U and some C and A (or G) as bases.

So our poly peptide can be

AUG-UUU-UUC-UCU-UUU-UCU-UUU-UUA-UUC-CUU-UUC- UCU-UAA

Met- Phe- Phe- Ser- Phe- Ser- Phe- Leu- Phe- Leu- Phe- Ser- STOP

Other amino acids such as AUG- Met, UAU for amino acid Tyr, UGU for Cys in small amount will also be encoded by this polypeptide.

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