The amino acid that becomes attached to a molecule of transfer RNA is specified by a...

• A. Anticodon
• B. Codon
• C. Nucleotide
• D. Amino acid

Answer: (B)

The genetic code links mRNA triplets to specific amino acids, and transfer RNA acts as the adapter carrying the correct amino acid to the ribosome. Each mRNA codon specifies which amino acid should be added, and the tRNA that recognizes that codon is charged with that amino acid by the appropriate enzyme. The anticodon on the tRNA ensures proper base pairing with the codon, but it is the codon’s identity that determines which amino acid is loaded onto the tRNA. A nucleotide on its own or the amino acid itself aren’t what specify the attachment; the codon in the mRNA is.