This chapter begins by reviewing the foundational elements of genetics, including the structure of DNA, the universal genetic code, and the various types of mutations that create genetic diversity. It provides a useful background on the process of DNA replication, compares the key differences between DNA and RNA, and introduces the RNA world hypothesis as a theory for the origin of life. Drawing on several well-known examples, we explore the link between specific mutations and the traits they cause. Finally, we illustrate how the interplay of inheritance, the continuous introduction of mutations, and the process of natural selection together serve as the primary mechanisms driving evolution.