Which of the following mutations would cause a premature stop codon?

A nonsense mutation is the correct choice because it specifically involves a change in the nucleotide sequence that leads to the creation of a premature stop codon. This occurs when a single nucleotide change in the DNA sequence alters the codon such that it encodes a stop signal instead of an amino acid. As a result, translation of the mRNA is terminated earlier than expected, leading to a truncated protein that is often nonfunctional.

In contrast, a silent mutation does not change the amino acid sequence, as it alters a nucleotide but still codes for the same amino acid due to the redundancy of the genetic code. A missense mutation results in the substitution of one amino acid for another, which may affect protein function but does not result in a premature stop. An insertion mutation typically adds one or more nucleotides into the sequence, which could potentially lead to a frameshift that might create a premature stop codon, but it does not guarantee this outcome in every case. Thus, a nonsense mutation directly leads to premature termination of protein synthesis, making it the most relevant answer here.