Developments in Brief : Tests Point Way to Day When Genetics Can Produce Disease-Free Chickens

Scientists have completed successful experiments in which the genes of a selected virus were passed on to new generations of chickens, and the achievement “brings closer the day when geneticists can custom-design chickens to resist disease, lay bigger eggs or have other traits valued by producers,” said Lyman B. Crittenden, a U.S. Department of Agriculture geneticist.

Until now, researchers had succeeded in getting only one vertebrate--the mouse--to pass on to its offspring viral genes inserted in the laboratory, according to Crittenden and a colleague, microbiologist Donald W. Salter.

In the latest experiments, the virus was inserted through the eggshell of embryos which later hatched and were bred with virus-free chickens, Salter said. So far, the genes have been inherited by three generations of descendants from that first pairing.

The virus involved, avian leukosis, causes a common disease of poultry. It was used because it is a retrovirus, which invades a cell’s own genes to “trick” the cell into producing more virus particles.

Crittenden said that eventually it may be possible to turn the virus against itself, making it self-destruct. It may also be possible to transport other useful genes into chickens.

While changing the genetic inheritance of animals is not new, it has always been done through breeding, by mating animals that have desirable traits, he said. Chickens and other animals could someday have custom-inserted genes to control growth and other functions, Crittenden said.