RNA Editing

Like a writer’s first draft, many RNA molecules require a bit of editing before they are ready to go into action. Remember that an RNA molecule is produced by copying DNA. Surprisingly, the DNA of eukaryotic genes contains sequences of nucteotidea, called Introns, that are not involved in coding for proteins. The DNA sequences that code for proteins are called exons because they are ‘expresaeC in the synthesis of proteins. When RNA molecules are formed, both the introns and the emns are copied from the DNA. However, the introna are cut out of RNA molecules while they are still in the nucleus. The remaining exona are then spliced back together to form the final mRNA. Why do ceLls use energy to make a large RNA molecule and then throw parts of it away? That’s a good question, and biologists still do not have a cmplete aoawer to it Some RNA molecules may he cut and spliced in different ways in different tissues. making it poasible for a single gene to produce several different forms of RNA. Introna and exoos may aLso play a role in evolut ion. This would make it possible for very small changes in DNA aequences to have dramatic effects in geoe expression.

RNA Editing