RNA is much shorter than DNA. DNA contains the code for making lots and lots of different proteins. Messenger RNA contains the information to make just one single polypeptide chain - in other words for just one protein, or even just a part of a protein if it is made up of more than one polypeptide chain.
DNA contains codes for making lots of different proteins, while RNA only contains the info to make one single protein, or just a part of a protein if it is made up of more than one other protein.
