The study of genetics—the inheritance of traits in living organisms—is a basic concept in biology. The same processes that provide the mechanism for organisms to pass genetic information to their offspring lead to the gradual change of species over time, which in turn produces biodiversity (the variety of life and the genetic differences among living organisms) and the evolution of new species. An understanding of genetics is becoming increasingly important as genetics research and technology—and the controversies surrounding them—gain greater influence on social trends and individual lives.

Rapid and revolutionary advances in genetics, medicine, and biotechnology have created new opportunities as well as a complex and far-reaching range of legal, ethical, and social issues. Genetic testing to screen for disease susceptibility, moral questions about the cloning of human organs, and the debate over genetically modified foods will affect many lives. To fully appreciate the benefits, risks, and ramifications of genetics research and to critically evaluate the related issues raised by ethicists, scientists, and other stakeholders, it is vital to understand the fundamentals of genetics, a discipline that integrates biology, mathematics, sociology, medicine, and public health.

In order to understand genetics, the development of organisms, and the diversity of species, it is important to learn how deoxyribonucleic acid (DNA) functions as the information-bearing molecule of living organisms. This chapter contains definitions of basic genetics terms such as DNA, chromosomes, and proteins, as well as an introduction to genetic concepts and processes including reproduction and inheritance.