Jaenisch’s first breakthrough occurred in 1974, when he and Beatrice Mintz showed that foreign DNA could be integrated into the DNA of early mouse embryos They injected retrovirus DNA into early mouse embryos and showed that leukemia DNA sequences had integrated into the mouse genome and also into that of its offspring.
Jaenisch’s initial accomplishment took place in 1974, when he and Beatrice Mintz successfully demonstrated the ability to fuse alien genetic material with the nascent DNA of early mouse embryos They employed retrovirus DNA to introduce foreign sequences into early mouse embryos, which subsequently integrated leukemia DNA into both their own genome and that of their progeny.