It is called an analogous structure, because they both have the same uses.
Answer: cancer or genetic disorders
It was the structure of DNA. Watson and Crick stole the credit from a woman whose name I can't remember, but basically she took really long exposure photographs (24 hours for some) and saw an X shape, which was the corresponding sign of a double helix. It was a pretty complicated method she was using and nobody had thought of using it for DNA research until then.
True, cells are the building blocks of life on earth
