Dave, we know that the genetic code is made up of DNA. DNA is the double helix that zips apart to make new copies of itself. DNA is just information. Somehow this information must be used to make proteins. This is where messenger RNA comes in. RNA is a single strand of information compared to the double strand of DNA.
mRNA picks and chooses the information from the DNA that will be expressed in the form of a protein. It now appears that the process of picking and choosing which information will be expressed in the form of a protein is at least as important as is the DNA code for the protein itself.
