Answer:
Friedrich Mieschers was a Swiss physician who discovered the DNA from white blood cells.
Hence, the contribution of Friedrich Mieschers for the genetic code is that he isolated and observed the DNA. DNA is the material from which the genetic code is made.
Friedrich discovered that the white blood cells have a substance called nuclein which is present in the nucleus of an atom. He discovered that this substance was acidic in nature and contained phosphates hence, it could not be a protein.