In a diploid organism, the DNA encoding one of the tRNAs for the amino acid tyrosine is mutated such that the sequence of the anticodon is now 5?-CTA-3? instead of 5?-GTA-3?
What kind of aberration in protein synthesis will this tRNA cause? Explain your answer.
If the DNA sequence specifying the anticodon is changed from 5?-GTA-3? to 5?-CTA-3?, this tRNA will now pair with the 5?-UAG-3? codon (instead of 5? -UAC-3?). The UAG codon normally serves as a stop codon. Thus, this change will result in the amino acid tyrosine being incorrectly incorporated where there is a stop codon, resulting in the addition of amino acids at the end of proteins that normally would come to a stop because of the UAG codon in the mRNA. (Note that the tyrosine codons will NOT cause premature termination of translation, as tyrosine should continue to be incorporated into proteins, as there are additional tyrosine-tRNA genes in the cell that will provide a normal supply of tyrosine-tRNAs.)
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