In what type of mutation is the resulting protein functionally unchanged due to no change in the amino acid sequence?

A silent mutation is a specific type of mutation that alters a DNA sequence without changing the amino acid sequence of the resulting protein. This happens due to the redundancy in the genetic code, where multiple codons can code for the same amino acid. Therefore, even if there is a mutation in the DNA that changes one nucleotide in a codon, it may still code for the same amino acid, leading to no functional change in the protein.

For example, if a codon changes from UUA to UUG in mRNA, both still code for the amino acid leucine. As a result, the overall structure and function of the protein remain unchanged despite the mutation at the nucleotide level.

Other types of mutations such as missense mutations lead to a change in a single amino acid, potentially altering the protein's function. Nonsense mutations introduce a premature stop codon, which truncates the protein, often inactivating it. Point mutations can refer to any change in a single nucleotide, which may result in missense, nonsense, or silent mutations, depending on the outcome of that change. Hence, the defining characteristic of a silent mutation is that the amino acid sequence remains the same, keeping the protein functionally unchanged.