What defines a silent mutation?

A silent mutation is defined specifically as a mutation that does not change the amino acid produced by a codon during the process of protein synthesis. This occurs because of the redundancy in the genetic code, where multiple codons can code for the same amino acid. For example, if a codon changes from UUA to UUG, both still code for the amino acid leucine, and thus there is no change in the protein's primary structure or function. Silent mutations can occur in the DNA sequence but do not impact the overall protein structure, allowing the organism to maintain normal function despite the genetic alteration.

In contrast, options referring to mutations that introduce a stop codon, alter protein function, or result in a frame shift directly impact either the protein's production and structure or its expression in significant ways, leading to profound changes in the resultant proteins.