Which mutation type refers to the addition of one or more nucleotide pairs to a gene?

The type of mutation that involves the addition of one or more nucleotide pairs to a gene is referred to as an insertion. This process can alter the length of the DNA sequence and can affect protein synthesis if it occurs within a coding region. Insertions can lead to protein products that may have altered functionality, depending on where they occur within the gene and how they impact downstream sequences.

While other mutation types such as deletion, substitution, and frameshift mutations are also significant in molecular biology, they have different mechanisms and effects on genetic material. For instance, deletions remove nucleotide pairs, while substitutions replace one nucleotide with another. Frameshift mutations, which often result from insertions or deletions, change the reading frame of the genetic code, but they specifically refer to the consequence of such insertions or deletions.

Overall, the key characteristic of an insertion is the addition of nucleotide pairs, which is why it is the correct term for this type of mutation.