What term refers to a rare change in the DNA of a gene that creates genetic diversity?

Mutation refers to a rare change in the DNA of a gene that can lead to genetic diversity. Mutations can occur naturally through various processes, such as errors during DNA replication or due to environmental factors. When mutations happen in the DNA sequence of a gene, they can result in new traits or characteristics that can be passed on to future generations if they occur in reproductive cells. This genetic variability is crucial for the process of evolution, as it provides a substrate upon which natural selection can act, enabling populations to adapt over time.

The other terms relate to DNA and genetics but do not specifically refer to the creation of genetic diversity through changes in the DNA sequence. Variation generally describes the differences among individuals in a population, expression refers to the process by which information from a gene is used to synthesize a functional gene product (like proteins), and replication is the process by which DNA makes a copy of itself. Hence, mutation is the most accurate term that directly addresses the concept of changes in DNA contributing to genetic diversity.