Question

Your friend is studying the effects of a mutation in the ORF of a gene. The mutation, which changes an A to a T occurs toward the center of the gene. Your friend scans the corresponding region of the mRNA and finds it results in 5’…GGGCTAUACUAUCCGCGA…3’ becoming 5’…GGGCTAUACUAACCGCGA…3’ with the changed base underlined. He hypothesizes that UAU encoding for Tyr is replaced by UAA encoding STOP due to this mutation. Disappointed, he finds that the mutant protein is the same size as the WT and the mutant individuals have no difference in phenotype. What mistake did he make?

Answer 1

usually we can find several options for this question such as, the codon is not present in the correct ORF, the codon might be present in the intron, etc.

however, in this question, it is clearly mentioned that the given region is of ORF, and the region is of mRNA.

So, the only option left with us is the bacteria may be suppressor strain, I.e, the bacteria contains a suppressor tRNA that recognizes STOP codon but codes for tyrosine amino acid.

suppressor tRNA is the one which contains anticodon for a STOP codon but has an amino acid. usually, tRNA suppressor for tyrosine are common in laboratory practices.