Gene

A gene is a unit of inheritance conferring a specific characteristic. The genetic unit is a segment of DNA or RNA (virus) located in a very specific place (locus) on a chromosome. Each DNA region which produces a molecule of functional RNA is a gene.

The cell nucleus is the "library" which contains all of a person's inherited pedigree. The chromosome is a "book" in this library and the gene is a "page" of this book.