The Department of Dominant Gene Conservation is a storehouse of DNA samples of the I-Jin of history. It is also referred to as the Dominant Genes Preservation Office.

The R.O.D. the TV reveals that department was conceived when it was discovered the Mr. Gentleman's body was deteriorating. Unable to find ways to heal or regenerate his current body, the British Library established the Department of Dominant Gene Conservation in order to gather the DNA of famous historic figures and use them to create a new suitable body for Mr. Gentleman. Its true purpose was kept hidden from most members of the British Library, save those of the highest authority.

Though progress was going well, at some point, the Department was attacked and destroyed by Dokusensha, the chief rival of the British Library. Several DNA samples were stolen and used to create the I-Jin. However, Dokusensha was unable to use the I-Jin to achieve their own goals to thwart the British Library; the I-Jin, led by Ikkyu, subsequently instigated the Great Man Incident.

Unable to use the DNA gathered by the Department and with Mr. Gentleman's impending and unavoidable death, the British Library resorted to their final plan in order to preserve Mr. Gentleman's personality, within seven books, until they could either find or create a suitable body for his rebirth.

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