Suppose there is a gene called VID that codes for the incredible ability to play

Question

Suppose there is a gene called VID that codes for the incredible ability to play any video game. This gene is 360 nucleotides long, with no introns. The wildtype version codes for a protein consisting of 120 amino acids. Some people cannot play video games well at all. Their VID gene was isolated and sequenced and found to have a nonsense mutation. The resulting non-functional VID protein consisted of just 20 amino acids. However, some rare individuals who also carry this same nonsense mutation in their gene do have a functional VID protein consisting of the full 120 wildtype amino acids. Which of the following most likely accounts for these rare individuals with a mutation in their gene but a fully functional protein.

a.The DNA of these individuals undergo crossover during mitosis and restore the genetic code of the original VID gene.

b.The mRNA of these rare individuals is repaired during post-translational modification, adding a 5’ CAP and a 3’ poly-A tail, restoring the normal coding sequence.

c.These rare individuals contain a tRNA anticodon with a mutation that recognizes the mutant mRNA codon as the original target codon, restoring the correct amino acid sequence.

d.These rare individuals contain an exceptionally high functioning DNA polymerase I N-terminal proofreading domain, allowing errors in the DNA to be fixed before damage occurs.

Explanation / Answer

The most likely outcome is option c) These rare individuals contain a tRNA anticodon with a mutation that recognizes the mutant mRNA codon as the original target codon, restoring the correct amino acid sequence.

Explanation - A nonsense mutation is one in which a single nucleotide change produces a stop codon instead of wild type amino acid. Protein synthesis terminate at stop codon as there is no tRNA anticodon for a stop codon. If tRNA anticodon mutates, it identifies a different amino acid.

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