What type of genetic mutation results in a change in the amino acid sequence of a protein without altering its function?

The correct answer highlights a silent mutation, which is a specific type of genetic mutation that results in a change in the DNA sequence but does not affect the amino acid sequence of the protein. This occurs due to the redundancy in the genetic code; several codons can encode for the same amino acid. Therefore, even if the DNA sequence has changed, the end result—the amino acid sequence—remains the same, often maintaining the protein's functionality.

In contrast, other types of mutations, such as nonsense mutations, introduce changes that typically lead to a premature stop codon, resulting in truncated proteins that are often nonfunctional. This would definitely alter the phenotype as well as the functionality of the expressed proteins. Thus, the nature of silent mutations allows for genetic variation without impacting the proteins' structure or function, which is why this answer accurately reflects the situation presented in the question.