Final answer:
A gene is correctly described as a unit of heredity, a segment of DNA influencing traits, and a segment producing a functional product, but not as an entire chromosome or as the complete information set of a cell.
Step-by-step explanation:
The correct descriptions of a gene are that it is a unit of heredity and a segment of DNA that influences one or more traits of an organism, as well as a segment of DNA that produces a functional product. However, it is not an entire chromosome nor the complete set of information inside a cell. Genes are the fundamental units of heredity, linearly arranged along chromosomes, and they specify the sequences of amino acids that form proteins, which in turn are responsible for nearly every function of the cell. Therefore, the options a, d, and e are the correct descriptions of a gene.