Final answer:
A single base substitution in DNA, such as an A replaced by a G, results in a point mutation, which is a kind of mutation affecting only one nucleotide pair. These alterations either do not change the protein, make minor alterations to it, or significantly impact its function. Frameshift mutations, which change the reading frame of the genetic code, are distinctly different from point mutations.
Step-by-step explanation:
When a single base in DNA is substituted with another base, such as an A being replaced by a G, the type of mutation that occurs is known as a point mutation or substitution. This kind of mutation affects only a single nucleotide and is the most common form of nucleotide mutation. Point mutations include the terms transition and transversion, with transitions involving a purine being replaced by another purine or a pyrimidine replaced by another pyrimidine, and transversions involving a purine replaced by a pyrimidine or vice versa.
A point mutation might result in a silent mutation, which does not change the amino acid sequence of a protein, or it can alter an amino acid, potentially impacting the structure and function of the protein synthesized. However, point mutations should not be confused with frameshift mutations, which are caused by insertions or deletions of nucleotides that change the reading frame of the genetic code.