A gene is a segment of nucleic acid that contains the information necessary to produce a functional product, usually a protein. Genes consist of a long strand of DNA (RNA in some viruses) that contains a promoter, which controls the activity of a gene, and a coding sequence, which determines what the gene produces.he bases Adenine(A) and Guanine(G) are Purines; while Thymine (T) and Cytosine (C) are Pyrimidines. Genes are poly-nucleotides. Each nucleotide is made up of a base group, a sugar and one ore phosphate groups. The sugar group forms the backbone of DNA.