Final answer:
rRNA does not determine the amino acid sequence in protein synthesis; this role belongs to mRNA, which is translated by tRNA molecules that bring specific amino acids to the ribosome based on codons. rRNA functions structurally within the ribosome and catalyzes peptide bond formation, not amino acid selection.
Step-by-step explanation:
rRNA does not dictate the amino acid sequence during protein synthesis, as its role is more structural and catalytic within the ribosome. The actual determination of amino acid sequence is instead dictated by messenger RNA (mRNA), through the intermediary of transfer RNA (tRNA). Each tRNA molecule brings a specific amino acid to the ribosome based on the corresponding three-nucleotide codon it recognizes on the mRNA strand. This recognition is ensured by the accuracy of the aminoacyl-tRNA synthetases (ARS) that charge tRNA molecules with the correct amino acids. The genetic code embedded within the mRNA sequence represents a series of codons; each codon specifies which amino acid will be added next to the growing polypeptide chain.
The evolution of the translation system from an RNA-only world to one that includes proteins shows a shift in specific roles, with rRNA taking a backseat in terms of direct genetic code interpretation. Structural analyses reveal that ARS and modifications within the translation machinery have tailored and evolved recognition systems that improve translation efficiency and protein diversity rather than rRNA itself binding or recognizing amino acids directly. rRNA's contribution to the protein synthesis, aside from its structural function, includes its enzymatic action in facilitating the formation of peptide bonds, rather than selecting amino acids.