Spatial genetic multiplicity

Spatial genetic multiplicity was what the Tenth Doctor used to explain how Gwen Cooper and Gwyneth looked similar. (TV: The Unquiet Dead, Journey's End)

Behind the scenes

 * Russell T Davies addressed spatial genetic multiplicity, explaining it as "It's not familial as we understand it. There's no blood tie. Spatial genetic multiplicity means an echo and repetition of physical traits across a Time rift."