passenger pigeon genome. As of now, Church is still unable to put together an entire genome from just these pieces of DNA, but he has invented technology that makes it possible for him to create sizable blocks of any DNA sequencing he wants.
This means that he could theoretically fabricate genes for traits unique to the passenger pigeon, such as its long tail, and splice them into the genome of a stem cell for a band-tailed pigeon using CRISPR, a type of DNA-editing technology. Scientists could then transform these stem cells into germ cells, which they could inject into the egg of a band-tailed pigeon. The birds hatched from these eggs would still be regular band-tailed pigeons, but their eggs and sperm would be packed with this new DNA. Once these birds mated, they would have children that carried the traits put into the DNA. These resulting pigeons could then be interbred, with the scientists hand-picking birds that looked more and more like the extinct species. This method of gene editing to bring species back is also far more realistic than finding a living nucleus, so Church is trying to use this to resurrect the wooly mammoth as well. Of course, breeding and raising these animals until there are enough of them to release into the wild would be a tremendous undertaking, but the monetary cost would be comparable to livestock breeding or conserving endangered wildlife. The expenses could be reduced by using genetic means to make the revived species more resilient, by boosting immunity and fertility. By making these animals more resilient, they are more likely to survive, and the scientists would not have to breed and raise as many.
In the end, while we have not entirely reversed extinction just yet, leading scientists such as George Church and Insung Hwang are getting closer to it every day. They have established new techniques to bring these vanished species back to life. Once our planet has finally regained the biological diversity and functions that these animals took with them when they disappeared, global warming would slow down immensely, and ecosystems could flourish once more.
References
Church, George. "George Church: De-Extinction Is a Good Idea." Scientific American, 1 Sept. 2013,
www.scientificamerican.com/article/george-church-de-extinction-is-a-good-idea/. Accessed 25 Oct. 2017.
Shultz, David. "Should We Bring Extinct Species Back from the Dead." Sciencemag.org, 26 Sept. 2016,
www.sciencemag.org/news/2016/09/should-we-bring-extinct-species-back-dead/. Accessed 26 Oct. 2017.
Worrall, Simon. "We Could Resurrect the Woolly Mammoth. Here's How." Nation Geographic, 9 July 2017,
news.nationalgeographic.com/2017/07/woolly-mammoths-extinction-cloning-genetics/. Accessed 1 Nov. 2017.
Zimmer, Carl. "Bringing Them Back to Life." National Geographic, Apr. 2013,
www.nationalgeographic.com/magazine/2013/04/species-revival-bringing-back-extinct-animals/. Accessed 27
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