The food safety of transgenic animals: implications from traditional breeding.

The genetic events associated with traditional selection have implications for the food safety of transgenic animals. Selection has been empirical, relying on the use of the best animals for breeding. Molecular techniques are now being used to identify the genes selected and to describe the differences between alleles that are important in selection to improve quantitative traits. The results of such analyses provide background details of the genetic and physiological effects of the traditional selection of animal lines. Examples of the kinds of genes that may be subject to selection are those coding for peptide hormones, steroid metabolic enzymes, the calcium-channel gating protein, and genes of the major histocompatibility complex. Unselected genes, sometimes with undesirable alleles, may be carried along as "hitchhikers" if they are closely linked to the selected gene. In spite of this potential for physiologically dangerous genetic changes in selected animals, hereditary food toxicity has never been associated with a selected line of the common food animals. This is probably because the allowable physiological range of results of selection is limited by the requirement for healthy, productive animals. Based on these limitations, foods from healthy transgenic animals produced for the purpose of herd improvement are likely to be as safe as the foods from the untransformed parental line. Animals are important indicators of their own food safety.