Purestrain Genestealers are fifth-generation descendants of Genestealer hybrids, carrying an identical genome to the original Genestealer. Genestealer hybrids, however, are the initial offspring of the Genestealer's reproductive cycle, inheriting traits from both the Genestealer and the host parent. Over time, these hybrids give birth to a new purestrain Genestealer, which carries some traits from the host species.