DNA Translatio3 - pairing with different bases The wobble...

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DNA Translation The Wobble Hypothesis The structure of the anticodon of tRNA helps to explain the degeneracy of the genetic code. Previously, in the SparkNote on the Genetic Code, we saw that more than one codon could specify a particular amino acid. However, now we know that tRNA acts as a go between for the codons of mRNA and amino acids. Each tRNA binds to a specific amino acid, but the anticodons of some tRNA molecules can bind to two or three different codons. The flexibility of some anticodons is the result of the fact that the 3' end of the anticodon is more spatially confined than the 5' end. As a result, the 5' end of the anticodon is free to hydrogen bond with several base groups located at the 3' position of the codon. This idea is called the wobble hypothesis and has been confirmed by X-ray studies that show that while the 3' and middle positions are held tightly in a specific orientation by stacking interactions, the 5' position is not. The 5' position is called the wobble position because it can move around to allow for its
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Unformatted text preview: pairing with different bases. 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....
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