Which mutation could potentially alter the entire reading frame of a gene?

A frameshift mutation has the potential to alter the entire reading frame of a gene. This type of mutation occurs when nucleotides are inserted into or deleted from the DNA sequence in numbers that are not multiples of three. Because the genetic code is read in triplets (codons), the addition or removal of nucleotides disrupts the grouping of the codons, leading to a shift in the reading frame. This shift can change every subsequent amino acid in the polypeptide chain from the point of mutation onward, potentially resulting in a completely different protein.

In contrast, point mutations typically involve a change in a single nucleotide base but do not necessarily disrupt the reading frame unless they occur at a specific position that results in a premature stop codon. Nonsense mutations introduce a premature stop codon which can truncate a protein, but it does not shift the reading frame. Missense mutations change one amino acid in a protein sequence but leave the rest of the sequence intact, hence they do not cause a complete rearrangement of the reading frame. Therefore, the nature of a frameshift mutation is what makes it especially significant in altering the overall output of a gene.