What type of mutation results in the substitution of one amino acid for another?

The correct response is related to the concept of missense mutations. A missense mutation occurs when a single nucleotide change in the DNA sequence leads to the incorporation of a different amino acid in the resultant protein. This type of mutation alters the codon in mRNA, which is then translated into a protein. Because the change involves a single amino acid, it can potentially affect the function of the protein, depending on the role of the substituted amino acid.

For example, if the original DNA sequence codes for an amino acid that plays a crucial role in the protein's active site, the substitution could significantly impact the protein's activity or stability.

In contrast, a silent mutation does not alter the amino acid sequence due to the redundancy of the genetic code, thus not impacting protein function. A nonsense mutation introduces a premature stop codon leading to truncated proteins that are usually nonfunctional. Lastly, an insertion mutation involves adding one or more nucleotides into the DNA sequence, which can result in a frameshift, altering the downstream sequence of amino acids and often leading to a completely different protein product.

Understanding these differences highlights the specific role that missense mutations play in genetic variations and their potential effects on protein structure and function.