This document provides an overview of mutations, which are heritable changes in genetic information that occur due to mistakes during DNA replication. There are two main types of mutations: gene mutations, which affect a single gene, 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. Mutations can have a variety of effects on genes and organisms, with some being harmful by disrupting gene function and others being beneficial by allowing organisms to adapt to new environments. Factors like environmental stressors and mutagenic chemicals can increase mutation rates.