You are studying the effects of chemical treatment of components of the translational machinery. You discover that one chemical in particular results in the conversion of the cysteine attached to a tRNA to alanine. Which of the following would best describe the results of this chemical-induced insertion of alanine into the resultant polypeptide?

Question

Quizplus · Accepted Answer

The chemical treatment changes the cysteine attached to tRNA to alanine, so alanine will be incorporated into the polypeptide where cysteine is normally coded for.  It is absolutely necessary that the discrimination of correct amino acid and correct tRNA be made by a given aminoacyl tRNA synthetase prior to release of the aminoacyl-tRNA from the enzyme. Once the product is released, there is no further way to proofread whether a given tRNA is coupled to its corresponding amino acid. Erroneous coupling would lead to the wrong amino acid being incorporated into the polypeptide, since the discrimination of amino acid during protein synthesis comes from the recognition of the anticodon of a tRNA by the codon of the mRNA and not by recognition of the amino acid. Desulfuration of cys-tRNAcys with Raney nickel generates ala-tRNAcys. Alanine is then incorporated into an elongating polypeptide where cysteine should have been.

You Are Studying the Effects of Chemical Treatment of Components