What is the definition of a mutation?

A mutation is specifically defined as a permanent change in the DNA sequence of an organism. This definition is critical because mutations can occur in many ways, such as through errors during DNA replication, exposure to mutagens, or through genetic recombination. These changes can affect a single nucleotide (point mutation) or larger segments of the DNA, potentially leading to variations that can be passed on to subsequent generations.

The permanence of this change distinguishes it from other types of modifications or alterations within the cell. In contrast, alterations in protein sequences may arise from mutations but are not synonymous; multiple mutations can lead to the same protein sequence due to redundancy in the genetic code. Similarly, changes in the cell membrane or shifts in gene expression can result from a variety of processes, but these are not classified as mutations since they do not involve a change in the underlying DNA sequence itself.