Final answer:
Transfer RNA (tRNA) is the molecule that acts as the translator between an mRNA codon and an amino acid, bringing specific amino acids to the ribosome to build a protein based on the sequence specified by mRNA.
Step-by-step explanation:
The molecule that serves as the "translator" or intermediary between an mRNA codon and an amino acid is transfer RNA (tRNA). tRNA molecules have anticodons which base pair with the codons of mRNA strands during the process of protein synthesis. Each tRNA carries a specific amino acid that corresponds to its anticodon, and when a tRNA molecule recognizes a codon on the mRNA, it brings the appropriate amino acid to the growing polypeptide chain. For example, if the mRNA has a codon sequence of CUA, the tRNA with a complementary anticodon of GAU would bind to it and contribute a leucine amino acid to the polypeptide chain. This translation of genetic information from mRNA to amino acids is crucial for the synthesis of proteins.