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The wobble hypothesis means that if the first and second positions are the same, certain different bases in the third position will code for the same amino acid. Codons that specify for the same amino acid are called "synonyms."

Loading Proteins onto tRNA

Before translation can occur, a molecule of tRNA must be bound with the appropriate amino acid. This two-step process is called "charging". In the first step, called adenylylation, an ATP molecule is hydrolyzed, releasing two phosphates, and, transfigured into AMP, forms a high-energy bond with an amino acid.

Figure %: Adenylylation
In the second step, the amino acid-AMP complex is bound to its specific tRNA molecule by an enzyme to form aminoacyl tRNA. There are twenty distinct enzymes engaged in the formation of aminoacyl tRNA, one for each amino acid. In the process of binding the tRNA and amino acid, the AMP is separated from the amino acid.

Specificity of Charging

The specificity of the charging reaction is maintained through two mechanisms. First, amino acids recognize the correct tRNA through distinguishing features on the tRNA, such as the acceptor stem, D stem, and anti-codon stem. Second, the entire process of charging is goverened by a proofreading system that ensures the appropriate amino acid has been loaded onto each tRNA molecule. The proof- reading mechanism checks the reaction at both steps to ensure proper pairing.

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