In the Sept. 10 letter "Beware Engineered Food," Charles Margulis expressed concern about the harmful effects of the use of "marker" genes, which code for antibiotic resistance.

If a plant has been engineered to contain a gene for antibiotic resistance, that doesn't make the person who consumes the plant resistant to antibiotics as well. If it were that easy to alter people genetically, we would have been able to cure many of our genetic diseases by now. Imagine. Just incorporate the insulin gene into a plant's genes and cure a diabetic by feeding him that plant. Sorry, it doesn't work that way.

A plant's genes, composed of DNA, are destroyed in our digestive tract. It doesn't matter where the genes came from originally either; they are just plant DNA now.

The fear of engineered food is a natural fear of the unknown. What is needed is an educational campaign for consumers, so people can understand what is involved in the process and then not fear the food. There are indeed good reasons for labeling genetically altered foods, such as possible new allergens for a few susceptible individuals.

If as many agrobusiness dollars went into public education as now go into advertising, and lobbying against labeling, perhaps people would become more comfortable with the food, and the food industry would not have to be so opposed to the labeling.

H. F. ELSON

Bethesda