There are a lot of genetically modified foods (by modern methods) in the market today (at least in the USA). All the foods we eat, were genetically modified by artificial selective breeding over centuries.
Here are my questions:
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If we take the original wild species (say teosinte for corn, or wild banana) and genetically engineer it to make the 19th century flint corn or banana, will all the other DNA be the same ? In other words, Will a GMO flint corn and a 19th century flint corn have 100% matching DNA or only the DNA parts that makes it visual/taste properties ?
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Artificial selection was carried out by humans over thousands of years and health /ecology detrimental effects were mitigated. Is there a scientific time limit (number of generations) before a modern GMO food can be considered safe for the ecology /human health ?
First of all, most fruits and vegetables are not produced with the aid of genetic modification technology (the short list includes corn, soybeans, papayas, sugar beets and some zucchini and summer squash). So by “a lot of genetically modified foods” you’re basically referring to processed foods.
There’s debate over how many genes have been involved in (for example) teosinte’s evolution into modern corn. Some think small changes occurred in many genes, while there have been recent studies suggesting major alterations in just a few genes occurred.
https://teosinte.wisc.edu/pdfs/Science-1991-CULOTTA-1792-3.pdf
Non-GM plant breeding has been carried out by various means, including slow artificial selection and radiation-induced mutations. By comparison to GM plant breeding, “conventional” breeding is largely unregulated, and there have been a few occasions where “conventional” breeding has resulted in detrimental health effects not seen in GM counterparts. For instance, some squash hybrids may have high levels of cucurbitacins which have made people sick.
Rather than worrying about what for decades has been a non-issue (GMO food safety), I’d be more concerned about food poisoning from unsafe growing and food handling practices, which affect both organic and non-organic produce.
I work tangentially in this area. At a symposium last year some plant physiologists and growers did a presentation on the process. They said it took 12 to 15 years to go from concept to fully tested. I’m not sure if that includes human consumption trials or not, or if that was just to ensure that the proper phenotypes were present in the crop. I believe that it does because I recall them saying that after a certain number of trials the growers were permitted to sell the produced crops. So, I don’t know for certain but that might be an answer.