X X_chromosome X_ray x-axis x-linked x-linked_dominant_inheritance x-linked_gene x-linked_recessive_inheritance x-linked_scid x-or_circuit X-radiation x-ray X-ray_diffraction X-ray_film X-ray_machine X-ray_photograph x-ray_photography X-ray_picture X-ray_therapy X-ray_tube X-raying x-scid