Chapter 14, Problem 17CONQ

Mutations in tRNA genes can create tRNAs that recognize stop codons. Because stop codons are sometimes called nonsense codons, these types of mutations that affect tRNAs are called nonsense suppressors. For example, a normal ${\text{tRNA}}^{\text{Gly}}$ has an anticodon sequence CCU that recognizes a glycine codon in mRNA (GGA) and puts in a glycine during translation. However, a mutation in the gene that encodes ${\text{tRNA}}^{\text{Gly}}$ could change the anticodon to ACU. This mutant ${\text{tRNA}}^{\text{Gly}}$ would still carry glycine, but it would recognize the stop codon UGA. Would this mutation affect attenuation of the trp operon? Explain why or why not. Note: To answer this question, you need to look carefully at Figure 14.12 and see if you can identify any stop codons that may exist beyond the UGA stop codon that is located after region 1.