Question

Met A gene for an elongator tRNA (anticodon 5'CAU decodes the AUG codon) was constructed on a DNA synthesizer, with the identical sequence of the native methionine tRNA gene with the exception that the anticodon was changed to 5'CUA (decodes the UAG amber triplet). This suppressor tRNA gene was introduced on a plasmid into a tryptophan auxotroph that contains an amber mutation in the gene for the enzyme anthranilate synthetase (the $trpE$ gene), required for tryptophan biosynthesis. Addition of the suppressor tRNA gene allowed the cell to grow in the absence of added tryptophan. When the anthranilate synthetase in the suppressed strain was sequenced, glutamine was found in the protein at the location where the amber mutation had originally occurred. Suggest an explanation for these results. [Hint: think about tRNA identity elements]

          Met
A gene for an elongator tRNA (anticodon 5'CAU decodes the AUG codon) was constructed on a
DNA synthesizer, with the identical sequence of the native methionine tRNA gene with the
exception that the anticodon was changed to 5'CUA (decodes the UAG amber triplet).
This suppressor tRNA gene was introduced on a plasmid into a tryptophan auxotroph that contains
an amber mutation in the gene for the enzyme anthranilate synthetase (the $trpE$ gene), required for
tryptophan biosynthesis.
Addition of the suppressor tRNA gene allowed the cell to grow in the absence of added tryptophan.
When the anthranilate synthetase in the suppressed strain was sequenced, glutamine was found in the
protein at the location where the amber mutation had originally occurred.
Suggest an explanation for these results. [Hint: think about tRNA identity elements]

Met
A gene for an elongator tRNA (anticodon 5'CAU decodes the AUG codon) was constructed on a
DNA synthesizer, with the identical sequence of the native methionine tRNA gene with the
exception that the anticodon was changed to 5'CUA (decodes the UAG amber triplet).
This suppressor tRNA gene was introduced on a plasmid into a tryptophan auxotroph that contains
an amber mutation in the gene for the enzyme anthranilate synthetase (the trpE gene), required for
tryptophan biosynthesis.
Addition of the suppressor tRNA gene allowed the cell to grow in the absence of added tryptophan.
When the anthranilate synthetase in the suppressed strain was sequenced, glutamine was found in the
protein at the location where the amber mutation had originally occurred.
Suggest an explanation for these results. [Hint: think about tRNA identity elements]

Added by Kenneth N.

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