Why does DNA mutations allows us to understand the traits observed in organisms

(look at the explanation below)

Explanation:

Genetics is the scientific study of inherited variation. Human genetics, then, is the scientific study of inherited human variation. A second reason for studying human genetics is its practical value for human welfare. In this sense, human genetics is more an applied science than a fundamental science. One benefit of studying human genetic variation is the discovery and description of the genetic contribution to many human diseases.