Genetic engineering : How to improve growth

Abstract

Recent development in molecular biology makes the isolation of virtually any gene possible. The isolated gene can be mutated, in vitro, to modify its genetic message or its regulatory elements. It can then be reintroduced into cells or into the whole organism (transgenesis) and a physiological function can thus potentially be modified. These possibilities have been and still are being applied to animal growth. Genes coding for GRF (Growth Releasing Factor), GH (Growth Hormone), and IGF1 (Insulin-like Growth Factor) have been introduced into embryos of various animal species. These transgenes were expressed and this led to an acceleration of growth and to an increase in animal size. This phenomenon was accompanied by significant changes in the metabolism of the animals. The fact that the expression of the transgenes used could not be modulated led to an over secretion of GH, which is responsible for various physiological disorders, rendering most of the transgenic animals expressing a GH transgene of low interest for production. Although transgenesis has become a routine experiment in a certain number of laboratories, it remains relatively difficult on a large scale using most domestic animals. Further studies on the mechanisms which control transgene expression and on methods leading to transgenesis must be conducted before genetic engineering can really contribute to an improvement in animal breeding.