I'm in the mid-game, and I've researched Gene Splicing, but for some strange reason, nutrient restrictions are still held down with a chain and iron ball. I'm assuming it's a bug, since I've recently boosted the resources of monolithes up a notch in alpha.txt. Anyone had this happen to them?
Most likely is something in the alpha.txt file - have you checked the nut restrictions string? The tech abbreviation must be spelt correctly - any typos in there and it won't work.