Final answer:
The mutations in question are categorized as indels (insertion-deletion mutations), which represent a type of frameshift mutation and cause significant alterations in the protein sequence if they are not in multiples of three nucleotides.
Step-by-step explanation:
The mutations described, such as c.1251_1252delGGinsTT, represent scenarios where two nucleotides are deleted and replaced with different nucleotides. These transformations do not conform to typical single nucleotide polymorphisms (SNPs), where only one base pair is altered without an accompanying deletion or insertion.
Instead, such mutations are classified as indels (insertion-deletion mutations). These are a type of frameshift mutation that has the potential to be more disruptive to the protein sequence than SNPs. Indels can shift the reading frame of the codons in an mRNA sequence, resulting in an altered sequence of amino acids translated, potentially leading to nonfunctional proteins or premature stop codons.
Given the importance of the triplets in the genetic code, an insertion or deletion that occurs in a multiple of three (like with the loss or addition of three nucleotides) may not alter the downstream reading frame, thus possibly resulting in a less deleterious effect as opposed to a single nucleotide insertion or deletion, which would invariably cause a frameshift alteration. Therefore, a frameshift mutation introduced early in the DNA sequence is likely to result in a more significantly altered protein than a similar mutation occurring later in the sequence.