Answer:
A base substitution occurs when a single nucleotide is replaced with another nucleotide. This can cause a change in the encoded amino acid, leading to an alteration in the protein's structure and function. An insertion or deletion of a base can disrupt the reading frame of the gene, resulting in a shift in the codons and a change in the encoded amino acid sequence in the protein. This can lead to a change in the protein's structure and function, and in some cases, the protein can become non-functional.