So RNA molecules are used to basically transcribe the information stored in DNA into a form that can be understood and read by that cell. So to build the protein we take the DNA, we essentially transcribe that information from the DNA into the RNA and now the RNA is used directly to form the proteins in the ribosomes. Now the other function of DNA is to actually pass down the genetic information from one individual to the offspring. So when we reproduce we replicate DNA molecules and pass those replicated identical DNA molecules or actually not identical, they are slightly different because of different types of variations but we pass them down into the offspring. And the second function of RNA is to actually assist in protein synthesis. So we have different types of RNA molecules.