A mutation that changes one codon to another codon encoding a different amino acid is called what?

• A. Silent mutation
• B. Missense mutation
• C. Nonsense mutation
• D. Frameshift mutation

Answer: (B)

A single-nucleotide change that makes one codon code for a different amino acid alters the protein’s amino acid sequence at that spot. This is called a missense mutation.

Codons specify which amino acids get added during translation, so changing the codon to another that codes for a different amino acid changes the primary structure of the protein at that position. The impact varies: the new amino acid might disrupt folding or function, or it might have little effect if it’s similar to the original.

In contrast, a silent mutation also changes a codon, but because of the genetic code’s redundancy, it still encodes the same amino acid, leaving the protein unchanged. A nonsense mutation changes a codon to a stop signal, truncating the protein. A frameshift mutation results from insertions or deletions that shift the entire reading frame, altering many downstream amino acids and usually producing a nonfunctional protein.