A synthetic mRNA transcript used in a gene-therapy trial contains a coding region of exactly 489 nucleotides. During the process of translation, ribosome complexes read the nucleotides in non-overlapping triplets known as codons. Each codon corresponds to a single amino acid, with the exception of the terminal stop codon, which terminates translation without contributing an amino acid to the polypeptide chain.
Assuming this transcript begins with a start codon and terminates with a single stop codon:
Determine the total number of codons in this mRNA transcript.
Calculate the final number of amino acids in the synthesised polypeptide chain.