Final answer:
A single nucleotide change in DNA can result in a silent mutation due to the genetic code's redundancy, potentially leaving the protein unchanged. Additionally, insertions or deletions of three nucleotides could still result in a partially active protein, highlighting the complexity of genetic mutations.
Step-by-step explanation:
If a single base is changed in the DNA sequence, such as from an A to a G, this is called a point mutation. A point mutation can have different outcomes depending on where it occurs and which nucleotide is substituted. One possible outcome is that the protein does not change at all, which is due to the redundancy of the genetic code. Each amino acid is coded by multiple codons, and this property is known as the 'degeneracy' of the code. Thus, if the changed base still results in a codon that corresponds to the same amino acid (a silent mutation), there is no change in the resulting protein.
Furthermore, Sidney Brenner and Frances Crick's experiments indicated that if three nucleotides are inserted or deleted, the resulting protein may still be functional. The reason for this is that three nucleotides make up a codon, which corresponds to a single amino acid. Therefore, such a frame shift mutation could result in a protein that is only slightly different from the normal version, possibly having reduced functionality but still being active.