Effects of Mutations - Protein Function - Silent Mutations - Missense

Some mutations don't have any noticeable effect on the phenotype of an organism. This can happen in many situations: perhaps the mutation occurs in a stretch of DNA with no function, or perhaps the mutation occurs in a protein-coding region, but ends up not affecting the amino acid sequence of the protein.
Mutations are changes in a DNA sequence, and they can occur due to radiation or other types of DNA damage. A point mutation is a change in one nucleotide or base pair of a DNA sequence. A silent mutation is a point mutation that doesn't lead to an amino acid change in the protein product.
In genetics, a missense mutation is a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid. It is a type of nonsynonymous substitution.