DNA program

A DNA program is a program that makes up the physical and mental characteristics of a Reploid. It is also referred to as "DNA data" or simply "DNA".

Characteristics
DNA programs obtained from bosses and enemies can be analyzed and utilized by X's Variable Weapon System, Zero's Learning Ability and Axl's Copy Ability. They can also be used to create power-up items for Reploids. Furthermore, utilizing DNA programs, the revival of deceased Reploids becomes possible, specifically by the use of a special type of DNA program called the "DNA Soul."

History
In Mega Man X6 it is revealed that the Nightmare can change DNA and AI programs. By changing these programs, the Nightmare causes both physical and mental changes in Reploids. In Mega Man X8 it is also implicated that the Sigma Virus changes DNA programs similar to the Nightmare; Alia explained that the Copy Chip makes Reploids resistant to viruses because it changes Reploid DNA.