Mutations are changes in genetic information that can occur when cells copy DNA. There are two main types: gene mutations, which involve changes in single genes, and chromosomal mutations, which involve changes to whole chromosomes. Gene mutations include point mutations like substitutions, insertions, and deletions. Chromosomal mutations involve changes in chromosome number or structure, such as deletions, duplications, inversions, and translocations. Mutations can have harmful effects by disrupting gene function, but can also have beneficial effects and allow organisms to evolve traits that help them adapt.