What role does transfer RNA (tRNA) play in protein synthesis?

Transfer RNA (tRNA) plays a critical role in protein synthesis by carrying specific amino acids to the ribosome, where proteins are assembled. Each tRNA molecule has an anticodon that pairs with a corresponding codon on the messenger RNA (mRNA) strand, ensuring that the correct amino acid is added to the growing polypeptide chain in the sequence dictated by the mRNA. This function is essential for translating the genetic code into functional proteins, as the ribosome facilitates the assembly of amino acids into a polypeptide chain, forming a protein according to the instructions encoded in the mRNA.

The other choices do not accurately describe the role of tRNA. For example, copying mRNA into DNA involves processes related to reverse transcription, typically performed by reverse transcriptase, and is not a function of tRNA. Transcribing DNA into mRNA is the role of messenger RNA synthesis, carried out by RNA polymerase during transcription, rather than tRNA. Forming the structure of ribosomes refers to ribosomal RNA (rRNA), which along with proteins forms the ribosomal structure, while tRNA specifically functions in the translation process by delivering amino acids.