hmmm learnt this bit last year... basically it ocmes down to the use of x-rays to created a mutated bread mould called i THINK neurospora, something like that, basically from this they realised that it lacked a certain enzyme which affected the biochemical activity of the organism. And so from this they concluded that for every gene was controlled by a certain enzyme, which was then changed to one gene one protein and then to one gene one polypeptide in the fact that both enzymes and proteins are made up of polypeptides, cuz polypeptides are like the building blocks of proteins and enzymes, however the main thing is that its one gene for one polypeptide in that protein coudl be one OR more polypeptide
THERE YOU GO!