Genetic modification
Deliberately rewriting the genes of a living thing: switching particular genes off, or adding genes from another species.
In 2012 Jennifer Doudna, Emmanuelle Charpentier and colleagues showed that a bacterial system called CRISPR-Cas9 can cut DNA at a chosen place[1]. Because the target is specified by a short piece of RNA, editing became far easier than with earlier methods, and several genes can be changed at once. The work won the 2020 Nobel Prize in Chemistry.
Pigs bred for xenotransplantation are a leading application. Genes that make targets for the human immune system are knocked out, and human genes that restrain rejection and blood clotting are added. In 2017 pigs were produced in which all 25 copies of a virus sequence hidden in the pig genome had been inactivated[2]. How many modifications are enough is still unsettled.
Related terms
- XenotransplantationTransplanting organs or tissues from animals into humans. Today the main candidates are kidneys and hearts from genetically modified pigs.
- Carbohydrate antigenA sugar chain on the cell surface that the immune system uses as a target. In xenotransplantation the key example is α-Gal, present in pigs but absent in humans.
- iPS cellA body cell, such as a skin cell, given back the ability to become many kinds of cell by introducing a handful of genes.