View germline genetic modification
Germline genetic modification is a form of genetic engineering which involves changing genes in eggs, sperm, or very early embryos. This type of engineering is inheritable, meaning that the modified genes would appear not only in any children that resulted from the procedure, but in all succeeding generations. Germline engineering is controversial because of its potential for human enhancement.
Germline genetic modification in humans is already being used on a small scale to allow infertile women with genetic defects in their mitochondria to have children. Healthy human eggs from a second mother are used. The child produced this way has genetic information from two mothers and one father. The changes made are germ line changes and will likely be passed down from generation to generation, and, thus, are a permanent change to the human genome.
Germline modification stands in contrast to somatic cell genetic engineering, which is not heritable. Somatic genetic engineering involves adding genes to cells other than egg or sperm cells. For example, if a person had a disease caused by a defective gene, a healthy gene could be added to the affected cells to treat the disorder. As of now, this is likely to take the form of gene therapy. The distinguishing characteristic of somatic engineering is that it is non-inheritable, e.g. the new gene would not be passed to the recipient’s offspring.