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Genetic engineering and genetic modification refer to the direct manipulation of an organism’s (human or non-human) genes. Genetic engineering works since traits come from the genes in a cell, and putting a new piece of DNA into a cell can produce a new trait. For example, crop plants can be given a gene from an Arctic fish, so they produce an antifreeze protein in their leaves which can help prevent frost damage.
Genetic engineering can be used on crops food so that they are more nutritious, stay fresher, have a greater yield, or are more resistant to pests and infection. Genetic engineering has led to synthetic human insulin and the production of new types of experimental mice such as the oncomouse (cancer mouse) for research.
Human genetic engineering is the modification of an human’s genotype with the aim of choosing the phenotype of a newborn or changing the existing phenotype of a child or adult. It is speculated that genetic engineering could be used to change physical appearance, metabolism, and even improve mental faculties like memory and intelligence. Once the genes responsible for a disease are found, theoretically gene therapy should be able to permanently cure the disease.
Genetic engineering has made conditions of aging and death targets for engineering solutions. Theoretically genetic engineering could be used to drastically change people’s genomes, which could enable people to regrow limbs and other organs, perhaps even extremely complex ones such as the spine. There is no qualitative difference (only a quantitative one) between, for instance, a genetic intervention to cure muscular atrophy, and a genetic intervention to improve muscle function even when those muscles are functioning at or around the human average (since there is also an average muscle function for those with a particular type of dystrophy, which the treatment would improve upon).
There is a difference between treating the disease in an individual and changing the genome that gets passed down to that person’s descendants (germ-line genetic engineering):
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.
Germline engineering 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 future generations. Germline engineering in particular is controversial because of its potential use for human enhancement.