By Adam Tseng
Bringing back species from the dead. Reviving exotic fauna that has been gone for years. Is it possible? The answer is: Scientists already have.
To accomplish this seemingly impossible feat, two methods are used.
The Pyrenean ibex, one of only a few extinct species that have been brought back from extinction by cloning.
Cloning
The first, developed as early as the 1990s, is cloning. By inserting the nucleus of a target animal’s body, or somatic cell, into the embryo of another developing animal, a clone of the target can be born. This is because the somatic nucleus contains all of the instructions for how to develop into the target animal, allowing for an exact copy of the animal to be created. This method is called somatic cell nuclear transfer, and for it to work, a complete set of DNA must be available from the target animal. Otherwise, the DNA will not produce a complete animal.
Scientists have been able to extract full DNA from recently extinct species such as the Pyrenean ibex. However, the process is still ridden with error, and most animals that are cloned die within a few years due to genetic defects that prove to be fatal. More importantly, however, full DNA is impossible to find in very ancient species, as DNA decays over time. Though there are some environments, such as extreme cold, where DNA can be partially preserved, it is still not enough to withstand the test of time, and scientists can only recover bits of DNA from dinosaurs, mammoths, and other prehistoric species.
It seemed for a moment that de-extinction would be just another scientific fantasy. It was - until the advent of the second method: CRISPR.
CRISPR CAS-9
CRISPR CAS-9 is a technique used to directly change the DNA of an organism. It was invented by studying bacteria’s response to viruses. When people get sick, the body not only makes immune cells to fight the viruses but also makes some to keep a record of the virus. Bacteria function in the same way, except their record-keeper, are CRISPR arrays, small segments of RNA that match a small portion of the virus’s genetic code. When the virus is detected, the bacteria recognize it and use the Cas-9 protein to cut up the virus, rendering it useless.
Scientists use the CRISPR CAS-9 system in the same fashion when editing genes. They create a short CRISPR array consisting of a simple strand of RNA that matches the part of the gene that they want to cut out. They use the CRISPR arrays to identify and target the gene segment, which is then removed using the Cas-9 protein. This method is highly precise, and it can be used to make any sort of edit to the molecular code that makes up an organism. Thus, if used extensively, scientists could freely change the genetic makeup of any animals or even resurrect new species. By using CRISPR CAS-9, scientists can overcome the hurdles presented by cloning in that they do not need a full set of DNA to bring back extinct species. They can gather the DNA of a related species and modify it with CRISPR DNA to produce the extinct species’ DNA. For the moment, this promising technique is held back by arguments over whether de-extinction is a good idea to begin with. However, the means are there, and resurrecting mammoths and dinosaurs may not be such a far-off idea after all.
References
YouTube, YouTube, www.youtube.com/.
Martín, Raúl, and Sergey Zimov. “Bringing Them Back to Life.” National Geographic, 13 Jan. 2017, www.nationalgeographic.com/magazine/2013/04/species-revival-bringing-back-extinct-animals/.
“What Are Genome Editing and CRISPR-Cas9? - Genetics Home Reference - NIH.” U.S. National Library of Medicine, National Institutes of Health, ghr.nlm.nih.gov/primer/genomicresearch/genomeediting.
“What Is CRISPR-Cas9?” Facts, The Public Engagement Team at the Wellcome Genome Campus, 19 Dec. 2016, www.yourgenome.org/facts/what-is-crispr-cas9.
“What Is CRISPR-Cas9?” Facts, The Public Engagement Team at the Wellcome Genome Campus, 19 Dec. 2016, www.yourgenome.org/facts/what-is-crispr-cas9.