Which molecule brings amino acids to the ribosome to be added to a growing protein?

• A. tRNA
• B. mRNA
• C. RNA polymerase
• D. Codon/Triplet

Answer: (A)

Translation relies on adaptor molecules called transfer RNAs. Each tRNA carries a specific amino acid and has an anticodon that pairs with a complementary codon on the messenger RNA. As the ribosome reads the mRNA, a tRNA enters at the A site, its amino acid becomes linked by a peptide bond to the growing polypeptide on the tRNA in the P site, and the ribosome then shifts, moving the tRNA with the chain to the P site and freeing the A site for the next tRNA. This delivery system ensures amino acids are added in the exact order dictated by the mRNA sequence.

The other options aren’t providing amino acids to the ribosome: mRNA carries the genetic code; RNA polymerase makes RNA; a codon is the three-nucleotide unit on mRNA that specifies an amino acid, not a carrier.