Description :
hundreds of thousands of protein sequences found in current databases, only a small percentage correspond to molecules that have actually been isolated by somebody or experimented upon. That’s because determiningthe sequence of a protein is much more difficult than sequencing DNA — but all the proteins that a given organism (whether microbe or human being) can synthesize are encoded in the DNA sequence of its genome. Thus, the smart shortcut that molecular biologists have been using is to read protein sequences directly at the information source: in the DNA sequence! This way, we can pretend to know the amino-acid sequence of a protein that has never been isolated in a test tube.