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Wednesday, March 12, 2003

I am a fanatical enthusiast for genetically modified foods and golden rice in particular (and an incorrigible cut and paster see below). Golden rice is rice modified to make beta carotene ( a precursor to vitamin A so named because there is a lot of it in carrots). It is appealing partly because vitamin A deficiency is common in people who eat a lot of rice which when unmodified contains very little vitamin A. Golden rice is a major technological success because it is very hard to make cells make beta carotene a small molecule made in many steps by many enzymes. It is much easier to make cells make one new protein. As far as I know (almost all the way to the tip of my nose) all other genetically modified plants make one new protein each. Hmm so I was thinking is there another stable with a problem. Well there is a staple which is part of a lot of dangerously unbalanced diets – corn. Corn has the highest yield of any grain but it is not good food for two reasons. One is that the main corn protein contains very little of two essential amino acids (lysine and argenine I think Don’t trust any of my “facts”). This means that unless corn is eaten along with legumes that the protein is just used to make energy (water carbon dioxide and Urea). I should have guessed that sukatash wasn’t making it on taste. Corn with more lysine and argenine is one of the big failures of the green revolution period of plant improvement. People refused to grow it because it had lower yield. The claim that it was healthier (which can’t be proved on the spot) did not convince poor farmers who have enough sense not to trust every stranger who claims to have an answer to their problems. I’m stumped. The only role I see for biotech is to make lima beans taste less awful.

There is another problem with living mainly on corn – pellagra or vitamin B-6 (pirodoxal phosphate and don’t trust my chemistry either) deficiency. Here part of the problem is that corn contains a protein which binds very tightly to B-6. People in central America have learned to mill corn with alkaline rocks which liberate some of the B-6. Hmmmm now this looks like a case for biotech (the culprit is a protein). Now getting rid of a gene is very hard (so far as I know not managed for grains or plants generally). It is possible to block expression of a gene with antisense RNA (same gene in backwards makes RNA which sticks to the message and keeps it from being translated into protein). It should also be possible to make corn produce an antibody which binds even tighter than B-6 to the place where B-6 binds. Sounds doable to me. I’m not sure how much this sticky protein is the main Pelagra problem.


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