It will move along these five structural genes. It will produce the mRNA and then the mRNA will be used by the ribosomes to produce the enzymes and then the enzymes will be used to produce the tryptophan amino acid. So this is usually what is happening within the cell because the cell is usually continually producing the tryptophan that is needed to produce the many different proteins and enzymes that are found within the cell. Now what happens when the concentration of tryptophan rises? Now let's suppose there is a very high intracellular concentration inside that cell. So the tryptophan concentration inside is very high in this case because we do have a lot of the tryptophan molecules.