I'm no biologist, but a good demonstration of the extent to which the same genes can have differing expression is found by considering the variety across all th

I'm no biologist, but a good demonstration of the extent to which the same genes can have differing expression is found by considering the variety across all the specialised cells in your body. Your brain cells and muscles carry the same DNA, but it is expressed very differently. If this is possible, then clearly more subtle changes are possible without altering the DNA also.