Ontario Grade 12 University Biology (SBI4U) Course Practice Exam

The attachment of a specific amino acid to tRNA is determined by the mRNA codon. During the process of translation, the ribosome reads the sequence of codons on the mRNA strand. Each codon consists of a sequence of three nucleotides that correspond to a specific amino acid. The tRNA molecules have anticodons, which are complementary sequences that match the codons found on the mRNA. When a tRNA anticodon pairs with an mRNA codon, it ensures that the correct amino acid, attached to the tRNA, is added to the growing polypeptide chain.

This mechanism is crucial for the accurate synthesis of proteins, as it establishes a direct relationship between the genetic code carried by mRNA and the sequence of amino acids in the resulting protein. The amino acid specified by the codon is based on the universal genetic code, where specific triplet combinations correspond to particular amino acids. This process is tightly regulated to maintain fidelity in protein synthesis, meaning that the codon in the mRNA directly dictates which tRNA (and thus which amino acid) is utilized in building the protein.