Which mutation type shifts the "reading" frame of the genetic message due to nucleotide insertion or deletion?

A frameshift mutation is a specific type of mutation that occurs when nucleotides are inserted into or deleted from the sequence of DNA in a way that changes the way the sequence is read during translation. The genetic code is read in sets of three nucleotides called codons, each of which corresponds to a specific amino acid. If one or more nucleotides are added or removed from the sequence and the number of nucleotides inserted or deleted is not a multiple of three, this causes a shift in the "reading" frame. As a result, all subsequent codons are misread, which can lead to a completely altered protein product, often with significant functional consequences.

In contrast, point mutations involve a change in a single nucleotide that might result in a different amino acid but does not shift the reading frame. Nonsense mutations specifically refer to a change in a codon that creates a premature stop signal in the protein translation process, while chromosomal mutations involve larger scale changes to the structure or number of chromosomes and do not specifically deal with the reading frame. Hence, the identification of frameshift mutations is crucial in understanding the impact of mutations on protein synthesis and the overall function of the genetic code.