Gene

A gene is the functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.

Sources:  image from the National Human Genome Research Institute (NHGRI) Genetic Illustrations; definition from the National Human Genome Research Institute (NHGRI) Glossary of Genetic Terms

More:  The DNA of eukaryotic organisms contains exons and introns. Exons are expressed regions of DNA that are translated into protein. Introns are intervening regions that are not translated into protein. The function of introns is not yet known.