What is a mutation?

A mutation is defined as a change in the DNA sequence that can affect gene function. This alteration may occur due to various factors, such as errors during DNA replication, exposure to certain chemicals, or radiation. Mutations can lead to changes in the protein that is produced by a gene, potentially resulting in new traits or variations within an organism. Depending on where the mutation occurs—whether in a coding region or a regulatory region of the DNA—it can have different effects on the organism's phenotype, ranging from benign to deleterious or even beneficial traits.

The other options do not accurately describe mutations. For instance, normal variations in DNA sequences are common and typically represent polymorphisms rather than mutations. While genetic diseases may result from mutations, the term "mutations" itself does not imply the presence of a disease, making that choice not applicable. Lastly, DNA replication is the process by which DNA is copied, but it is not inherently related to the definition of a mutation; rather, errors in this process can lead to mutations.