Clark's assistant

The assistant of Dr. Clark was a healthy Japanese woman who donated her egg cells for the Les Enfants Terribles project in the 1970s. Her egg cells were used for the cloning experiment that created Solid Snake and Liquid Snake, thus making her one of the twins' biological mothers, due to their inheritance of her mitochondrial DNA.

Behind the scenes
The idea of Solid Snake being of Japanese descent was originally given in the user's manual of Metal Gear 2: Solid Snake, in which he is described as Japanese-British. In Metal Gear Solid, this is remarked upon by the character Vulcan Raven, though the revelation that Snake was a clone of Big Boss made the previous game's account uncertain. In Metal Gear Solid 4: Guns of the Patriots, Dr. Clark's assistant is introduced to explain the exact circumstances of his Japanese heritage.