Gene Key 21 sits on the same numbering that Human Design and, before it, the I Ching use. It shares its number with Human Design Gate 21 ("Control Of Resources"), carried over intact from that system rather than derived independently, and beneath both lies I Ching hexagram 21, Biting Through. Rudd retained from Human Design the sixty-four positions, their King Wen hexagram numbers, the arrangement of the hexagrams around a zodiacal wheel, and the pairing of each key with a "programming partner" opposite it on that wheel; he set aside the bodygraph, the types and the strategies, and added the Shadow-Gift-Siddhi spectrum. Three datable layers therefore stack here and are best kept distinct: an ancient hexagram, a 1987 Human Design gate, and a 2009 Gene Keys reading.
Richard Rudd's own reading of Gene Key 21 moves from the shadow of Control, authority asserted over others out of anxiety, through the gift of Authority, a rightful governance of one's own domain and resources, to the siddhi of Valour. Rudd ties the arc to the key's I Ching correspondent, Hexagram 21, Biting Through, whose received image of decisively removing an obstruction lodged between the teeth he reads as authority correctly exercised rather than controlling force.