What is a mutation?

A mutation is defined as a change in the DNA sequence. This alteration can occur in various forms, including substitutions, insertions, or deletions of nucleotides. Mutations can happen naturally during DNA replication or can be induced by environmental factors such as radiation or chemicals. These changes in the genetic material can have a variety of effects on an organism, ranging from neutral to beneficial, or even harmful, depending on where the change occurs and how it affects gene function.

The other options relate to concepts in genetics, but they do not accurately define a mutation. A repeated sequence of nucleotides can refer to certain types of mutations, such as microsatellite expansions, but it does not encompass the broader definition of a mutation itself. A gene that codes for a protein is a fundamental component of genetics but is not a mutation in itself; it is simply a functional segment of DNA. A type of chromosomal rearrangement involves larger structural changes in chromosomes rather than the specific alterations of the DNA sequence that characterize mutations. Thus, the most comprehensive and accurate definition of a mutation is a change in the DNA sequence.