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.