Everyone has heard of the famous DNA macromolecule where our genes reside, but less well known is its cousin, the RNA macromolecule. Two different molecular machines produce copies of DNA for two different reasons. One machine copies the entire double helix for the purpose of duplicating the genome before the cell divides into two daughter cells. The other machine merely transcribes one of the two strands in the double helix, and only for a relatively short segment. This copy, or transcript, is an RNA, not DNA, molecule. If you remember only one thing about RNA it probably is that the RNA transcript is passed to the ribosome machine which translates RNA’s string of nucleotides into a string of amino acids which will become a new protein. For many years that was thought to be the main function of RNA—to carry information like a messenger from the DNA gene to the ribosome. Now, in spite of evolutionary theory, that has all changed. Read more