DNA, or deoxyribonucleic acid, is the genetic material of all eukaryotes, stored in cell nucleus. DNA is a double helix polymer made of four bases:

• adenine (A)
• guanine (G)
• cytosine (C)
• thymine (T)

The specific sequence of these four bases within a specific DNA molecule fragment make genes. Gene sequencing therefore is the determination of the particular order of these four bases within a targeted fragment of DNA molecule.