How does degeneracy reduce mutational impact?

• A. Any codon change always alters the amino acid, increasing the likelihood of mutation effects.
• B. It prevents any mutation from happening in protein-coding regions.
• C. It requires RNA editing to translate a different amino acid every time.
• D. Silent mutations may occur where a codon change does not alter the amino acid, preserving protein function.

Answer: (D)

Degeneracy in the genetic code means that multiple codons can specify the same amino acid. Because of this redundancy, many single-nucleotide changes in coding regions do not change the amino acid that is added during translation. Those changes are silent (synonymous) mutations, so the protein sequence remains the same and the protein’s function is preserved. The third nucleotide often plays the wobble role, making substitutions there especially likely to be neutral.

So, the mutational impact is reduced because a DNA change can occur without altering the amino acid sequence, buffering the organism against potential functional changes. It’s not that mutations never happen or that every change is translated into a different amino acid or requires RNA editing—that would misrepresent how the genetic code works. The key idea is that silent mutations can occur due to codon degeneracy, helping maintain protein function despite some DNA alterations.