When would mutation not be harmful?

Mutation would not be harmful when it does not affect the structure and function of the protein or when the mutation occurs in a non-coding region.

If a mutation does not result in a change in the amino acid sequence, it is known as a silent mutation and will not have any effect on the protein. This can occur when the mutation does not change the codon or when it changes the codon to one that codes for the same amino acid.

Furthermore, mutation in non-coding regions, such as introns or intergenic regions, is less likely to be harmful because these regions are not directly involved in protein synthesis or regulation.