What is the Difference Between Synonymous and Nonsynonymous Mutation?

🆚 Go to Comparative Table 🆚

The main difference between synonymous and nonsynonymous mutations lies in their impact on the amino acid sequence of a protein.

Synonymous mutations are point mutations that change one base pair in the RNA copy of a gene without altering the amino acid sequence of the protein. These mutations are often considered functionally silent and evolutionarily neutral. However, recent studies have shown that synonymous mutations might play a role in driving human cancers. One major force that acts on synonymous mutations is the codon usage bias (CUB).

Nonsynonymous mutations are nucleotide mutations that alter the amino acid sequence of a protein. These mutations can result in changes to the protein's structure and function, making them subject to natural selection. There are several common types of nonsynonymous substitutions, including:

  1. Missense mutations: Nonsynonymous substitutions that arise from point mutations in a single nucleotide, resulting in the substitution of one amino acid for another in the protein.
  2. Nonsense mutations: Mutations that change an amino acid in a protein to a stop codon, which ends synthesis of the protein at that location and shortens the length of the protein. These mutations are a subset of nonsynonymous mutations and are also referred to as replacement mutations.

Comparative Table: Synonymous vs Nonsynonymous Mutation

Here is a table comparing synonymous and nonsynonymous mutations:

Feature Synonymous Mutation Nonsynonymous Mutation
Definition A change in the nucleotide sequence that does not alter the amino acid sequence. A change in the nucleotide sequence that alters the amino acid sequence.
Functional Impact Functionally silent and evolutionarily neutral. Changes the protein sequence and is frequently subjected to natural selection.
Diversity Does not change the amino acid sequence, so it does not contribute to gene pool diversity. Increases gene pool diversity.
Natural Selection Not subject to natural selection, as it does not change the amino acid sequence. Subject to natural selection, as it changes the amino acid sequence.