What does the term 'mutation' most directly refer to?

The term 'mutation' most directly refers to the alteration in the structure of DNA. Mutations are specific changes that occur in the nucleotide sequence of an organism's genetic material, which can result from various factors such as errors in DNA replication, exposure to radiation, or chemical influences. These alterations can lead to changes in proteins and, subsequently, the traits expressed by the organism. While changes in physical characteristics or allele frequencies may be consequences of mutations over time, the core definition fundamentally centers on the direct changes to the DNA structure itself. Understanding mutations is essential in genetics as they can provide the raw material for evolution and have significant implications for genetic diversity and adaptation within populations.