What peptide would be made by translation from a synthetic mRNA made of the repeating dinucleotide CGCG…?

The question lacks options, the options are:

A. a polymer of arginine plus a polymer of alanine

B. the peptide Met–Arg–Ala–Arg–Ala…

C. a polymer of alanine: Ala–Ala–Ala…

D. a peptide containing alternating arginines and alanines

E. a polymer of arginine: Arg–Arg–Arg…

The answer is D

Explanation:

Translation is the second process of protein synthesis (gene expression) where the mRNA molecule produced during transcription is used as a template for the synthesis of amino acid sequences, which species a particular polypeptide.

The nucleotides in the mRNA are read in a group of three in the ribosome. This triplet nucleotide is called CODON. Each codon specifies a particular amino acid and a collection of all codons constitutes the GENETIC CODE. Hence, in a case where dinucleotide CG is repeated in a sequence. The sequence will read:

CGC GCG CGC GCG CGC GCG

In the genetic code, codon CGC and GCG codes for arginine and alanine amino acids respectively. Therefore, if the CG dinucleotide keeps repeating, the nucleotides will be read three at a time, and the amino acid sequence will alternate between those two amino acids (Arginine and Alanine).

So we would have a peptide sequence looking like:

Arg-Ala-Arg-Ala-Arg-Ala-Arg