changing the genome of a close living relative to resemble the extinct one and is currently being attempted with the passenger pigeon. Genes associated with the woolly mammoth have been added to the genome of an African Elephant, although the lead researcher says he has no intention of using live elephants. Humans Gene therapy uses genetically modified viruses to deliver genes which can cure disease in humans. Although gene therapy is still relatively new, it has had some successes. It has been used to treat genetic disorders such as severe combined immunodeficiency and Leber's congenital amaurosis. Treatments are also being developed for a range of other currently incurable diseases, such as cystic fibrosis, sickle cell anemia, Parkinson's disease, cancer, diabetes, heart disease, and muscular dystrophy. These treatments only affect somatic cells, which means that any changes would not be inheritable. Germline gene therapy results in any change being inheritable, which has raised concerns within the scientific community. In 2015, CRISPR was used to edit the DNA of non-viable human embryos. In November 2018, He Jiankui announced that he had edited the genomes of two human embryos, to attempt to disable the CCR5 gene, which codes for a receptor that HIV uses to enter cells. He said that twin girls- Lulu and Nana, had been born a few weeks earlier, and that they carried functional copies of CCR5 along with disabled CCR5 (mosaicism), and were still vulnerable to HIV. The work was widely condemned as unethical, dangerous, and premature. Fish Genetically modified fish are used for scientific research, as pets, and as a food source. Aquaculture is a growing industry, currently providing over half of the consumed fish worldwide. Through genetic engineering, it is possible to increase growth rates, reduce food intake, remove allergenic properties, increase cold tolerance, and provide disease resistance. Detecting pollution Fish can also be used to detect aquatic pollution or function as bioreactors. Several groups have been developing zebrafish to detect pollution by attaching fluorescent proteins to genes activated by the presence of pollutants. The fish will then glow and can be used as environmental sensors. Pets The GloFish is a brand of genetically modified fluorescent zebrafish with bright red, green, and orange fluorescent color. It was originally developed by one of the groups to detect pollution, but is now part of the ornamental fish trade, becoming the first genetically modified animal to become publicly available as