Option C, "And these gene transfers could lead to a better understanding, if not a cure, for many different kinds of diseases."
Explanation:
Gene transfers have led to discovering of root cause of many genetic diseases specially the one that have only a single point mutation/monogenic diseases. The discovery of right cause of a disease can in turn help scientist to develop right treatment for it. For instance - Stem cell research has improved the ability of diseased person to fight with genetic diseases specially blood cancer etc.
