The answer is germline gene therapy.
The gene therapy is the process which aim is to introduce the gene for the desired protein into cells in order to make desired protein or to compensate for abnormal genes. If the gene for the desired protein is introduced into the gamete cells (eggs or sperms), then the gene therapy is called germline. The example is introducing the gene for bovine growth hormone into the eggs of pigs. This way the change is heritable and can be passed down to the next generation.