The RNA transcript that comes off the template DNA strand is known as the primary transcript, and it contains the genetic information of the gene that was transcribed. For protein-coding genes, this means that the primary transcript includes the information needed to direct the ribosome to produce the protein corresponding to the gene (Chapter 4). The RNA molecule that combines with the ribosome to direct protein synthesis is known as the messenger RNA (mRNA) because it serves to carry the genetic “message” (information) from the DNA to the ribosome. As we will see in this section, there is a major difference between prokaryotes and eukaryotes in the manner in which the primary transcript relates to the mRNA. We will also see that some genes do not code for proteins, but for RNA molecules that have functions of their own.