The thylacine: a case study
Despite successes in cloning mice and a small number of other currently living species, the possibility of successfully cloning an individual from the frozen remains of a woolly mammoth recently discovered in the Siberian permafrost or a 100-year-old alcohol-preserved thylacine (Tasmanian tiger) seems remote.
Tasmanian Museum and Art Gallery
For both these specimens, the first stage of the process — extracting DNA samples from the preserved tissue — has been achieved. From there the going gets tougher, even though the starting materials are far better than those available for the dinosaur cloning seen in the movie Jurassic Park.
In 1999, DNA was successfully extracted from an ethanol‑preserved Tasmanian tiger pup sample. In 2001, additional DNA was extracted from two other pups using tissue from bone, tooth, bone marrow and dried muscle.
In 2002, the Evolutionary Biology Unit at the Australian Museum in Sydney successfully replicated individual Tasmanian tiger genes using a process known as PCR. The next stage would have been to make copies of all the genes of the Tasmanian tiger to construct synthetic chromosomes. However, in 2005, the project was abandoned, because the DNA was found to be too degraded to work with effectively.
Producing viable embryos would be too difficult — perhaps even impossible — using the DNA preserved through freezing or in alcohol, as it is often damaged. Given the low efficiency of mouse cloning experiments, in which intact nuclei from living cells were used as the source of DNA for cloning, the likelihood of being able to clone an animal from a preserved specimen is extremely low with current technology.
Even if the difficulties with the technology were overcome, individuals produced from this alcohol-preserved specimen would all have exactly the same genetic make-up and would be the same sex — unless new genes could be artificially introduced into DNA from a thylacine in a museum.
All science is carried out in a social and economic context. A group of individuals like this could not make up a viable population. The idea of a lone and lonely mammoth or thylacine in a zoo or wildlife park is of concern to wildlife managers and to the community.
In 2008, scientists from the University of Melbourne extracted DNA from a 100-year-old thylacine pouch young specimen at the Victoria Museum. They managed to incorporate a small piece of DNA involved in the regulation of bone development genes into the genome of a mouse. The thylacine DNA functioned normally in the mouse cells. It was the first time that DNA from an extinct species has ever been used to induce a biological function in another living organism.
This type of work shows that even if a species is extinct, its genetic information is not lost. The function of genes from extinct animals can still be determined, revealing information about the evolutionary relationships of the animals and about how the particular genes evolved their particular functions.
The Australian Museum thylacine cloning project: http://www.amonline.net.au/thylacine/index.htm
Read about the closing of the project through ABC Science Online: http://www.abc.net.au/science/news/ancient/AncientRepublish_1304301.htm
Should we clone extinct species? - work sheet [PDF 33kb | 2 pages]
Try cloning a thylacine and bringing it back to life – interactive