What is the main characteristic of a silent mutation?

A silent mutation is characterized by a change in the DNA sequence that does not alter the resulting amino acid due to the redundancy of the genetic code. This means that although the nucleotide sequence might be different, the same amino acid is produced during translation, so the overall function of the protein remains unaffected.

This characteristic is crucial because it allows for variations in the genetic code without impacting the organism's phenotype or protein function. Silent mutations often occur in non-coding regions or may be synonymous codon changes where multiple codons can code for the same amino acid.

The other choices point to different types of mutations. Drastic alterations in protein function would typically be due to missense or nonsense mutations. The statement that silent mutations occur only in somatic cells is inaccurate, as they can occur in germ cells as well. Lastly, the creation of a premature stop codon defines a nonsense mutation, which leads to truncated proteins and often loss of function, contrasting with the subtle nature of silent mutations.