Tuesday, 23 October 2012

Resurrection: Extinction is NOT Forever

Resurrection: Extinction is Not Forever

Resurrection is a concept usually heard about in films and fantasy novels.  However, with recent technological advances, the possibility of bringing long extinct species back to life is becoming a reality.  The thylacine (aka Tasmanian tiger) was declared extinct in 1936 after the species was ruthlessly wiped out by farmers in collaboration with the Tasmanian Government.  In more recent years, as we begin to understand the importance of conservation, the general public has met the issue with guilt and regret, and have been madly trying to find any last vestiges of thylacine life still left in the wild with no success. As the technology making cloning possible has advanced, scientists have started to experiment with extinct species in an attempt to revitalize the population. 

Thylacine genes operating inside a
developing mouse fetus. (ABC News)
The Australian Museum made one such attempt in 1999, planning to bring the thylacine back from extinction.  Using a thylacine pup preserved in ethanol, dating back to the late 1890s , scientists collected DNA and attempted to find out if the dead DNA could still function inside a living animal- the first step to cloning a complete thylacine.  The DNA that could be contracted from the pup was extremely degraded due to the ethanol, making it difficult to experiment with the whole genome.  Instead, the researchers identified one segment responsible for the development of collagen, a protein involved in bone development.  This gene was attached to a blue marker and injected into a mouse egg, where it was incorporated into the genome of the developing mouse.  The effects of the gene can be seen in the image wherein the entire skeletal structure of the mouse appears to be formed by the thylacine gene. Fundamentally, the mouse had the same skeletal composition as the thylacine did a hundred years ago.   This serves to prove that DNA that has been dead for hundreds of years can still be functional in a host, opening doorways to further reincarnation projects.

Perfectly preserved mammoth calf.
(National Geographic)
However, attempting to clone long dead or even ancient DNA has hitches. Though DNA can typically remain stable for 10'000 years (meaning we won't be creating a Jurassic Park any time soon), it is rarely without damage.  The DNA of the thylacine pup was severely fragmented and degraded due to long exposure to ethanol and, as such, no further significant research could be conducted.  This issue is also present in even the most perfectly preserved extinct species, such as the Woolly Mammoth.  Another major issue with the degradation of ancient DNA is chromosomes.  At present, we have no idea how many chromosomes the thylacine may have had (due to the fragmentation of DNA), making it impossible to begin synthesising chromosomes.  Another problem with fragmented DNA is the issue of piecing it back together. Some extinct species, such as the New Zealand Moa, have genetic codes that consist of endless stretches of repetitive 'junk DNA', making it nigh impossible to reconstruct it.

If a perfectly preserved specimen was discovered, methods such as interspecies nuclear transfer, an already proven method of cloning, could be implemented and may be successful.  Without these perfectly preserved specimens the idea of resurrecting an extinct species is endlessly time consuming and extremely experimental.  Cloning is limited by the technology and skill available, so while the reality of seeing the Tasmanian tiger roaming the forests again is achievable, it is still many years away.

Luke Taylor

1. ABC News (2008), Tasmanian tiger DNA comes alive inside mouse, ABC News,<http://www.abc.net.au/news/2008-05-20/tasmanian-tiger-dna-comes-alive-in-mouse/2441920
2. Ogilvie, F. (2008), Scientists reincarnate thylacine DNA, ABC News, online audio, <yhttp://www.abc.net.au/news/2008-05-20/scientists-reincarnate-thylacine-dna/2443246>
3. Cox, T. Archer, M. (2008), The Science Show's Robyn Williams talks to researchers about the Thylacine DNA., ABC News, online audio, <http://www.abc.net.au/news/2008-05-20/the-science-shows-robyn-williams-talks-to/2441938>
4. Archer, M. (2008), University of New South Wales' Dean of Science Professor Mike Archer., ABC News, online audio, <http://www.abc.net.au/news/2008-05-20/university-of-new-south-wales-dean-of-science/2441942>
5. Dell'Amore, C. (2007) "Lovely" Baby Mammoth Found in Russia, National Geographics News, <http://news.nationalgeographic.com/news/2007/07/070711-mammoth-picture.html>
6. Maas, P.H.J. (2010). Cloning Extinct Animals. In: TSEW (2012). The Sixth Extinction Website. <http://www.petermaas.nl/extinct/articles/cloning.htm>

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