Final answer:
Frameshift mutations caused by insertions or deletions of nucleotides that are not a multiple of three can significantly affect gene function by shifting the reading frame. However, combining three 'plus' frameshift mutations can restore the reading frame to its original position, resulting in a functional gene. This is related to the triplet nature of codon reading because codons are groups of three nucleotides that specify each amino acid.
Step-by-step explanation:
Frameshift mutations, caused by insertions or deletions of a number of nucleotides that are not a multiple of three, are extremely problematic because they result in a shift in the reading frame. This means that every amino acid after the point of the mutation will be changed. In the case of three 'plus' frameshift mutations, the reading frame will be shifted back to its original position, resulting in a restored functionality of the gene. This is related to the triplet nature of codon reading because codons are groups of three nucleotides that specify each amino acid. When three nucleotides are added or removed, the reading frame is only shifted by one codon, allowing the rest of the protein sequence to remain intact and functional.