One of Australia's most celebrated species is the Thylacine or the Tasmanian tiger which became extinct, after the last known animal died in captivity at the Hobart Zoo, Tasmania, in 1936. Although called Tasmanian 'tiger' it belonged to the group of mammals called marsupials. Its extinction has since caused great outrage and remorse in the Australian society and government which were unable to curtail the illegal hunting down of the Thylacine. All known specimens from museums, universities or private collections have been recorded and photographed for compilation in the International Thylacine Specimen Database. Now, after almost a good sixty five years after its disappearance, efforts are being made to resurrect the animal from preserved samples.
The Australian Museum, Sydney began an ambitious cloning experiment in 1999 where the DNA from preserved specimens would be used to clone new individuals. If completed successfully, it could help bring back any extinct species. Since then, several samples from museum preserved specimens have been studied. In most of these cases, since hair is collected for analysis, no unsightly damage is done to the display and museum directors have been found to be enthusiastic. This has lead to the development of a new specialty christened by Stephan Schuster, a professor of Moleular Biology at Penn State, as 'Museomics'. Although there is some skepticism among the scientific community, it is heartening to note that some effort is being made to revive species lost to the world.
In 2002, DNA was extracted from the specimens stored in the museum and it was thought to be viable and capable of being replicated. However, after three years of tests, the DNA was found to be degraded and unviable.
In 2008, Andrew J. Pask and Marilyn B. Renfree from the University of Melbourne and Richard Behringer from the University of Texas successfully inserted the Col2A1 gene extracted from DNA of a hundred year old preserved thylacine specimen. This gene from these samples has been inserted into mouse embryo and been found to be expressed. By studying parts of the genome, a fair idea about the evolution of the species through time can be obtained and if these experiments are successful, it may even mean the revival of a long-lost species.
The samples used were taken from the preserved remains, more than a century old, stored in ethanol at the Victoria Museum in Melbourne. The DNA was extracted from these samples and a segment of the Col2a1 gene from this sample was into mouse embryo at the corresponding gene site. According to the scientists, "the thylacine DNA was resurrected, showing a function in the developing mouse cartilage which will later form the bone". This gene is responsible for bone development and hence the growth of healthy mice with the thylacine gene segment indicated the success of this experiment. This kind of gene expression experiment involving extinct species has never been performed before and is a step forward in conservation and preservation of the Earth's species.
In 2008, another group of scientists including Webb Miller and Stephan Schuster completed the sequencing of the thylacine mitochondrial genome using preserved specimens from the museum. This success indicates that it may be possible to sequence the complete genome of the thylacine. It has been reported that they ensured the accuracy of the sequencing data by 'independently determining each position in the sequences an average of 50 times'. Now, this success serves as an indicator that the genetic material from these specimens can be used to sequence the complete genome too.
The sequencing data has also helped to compare and study the position of the thylacine on the evolutionary tree. By the comparison of its genome to that of the numbat, a closely related species, they were able to conclude that the occurrence of low genetic diversity among endangered species may be a common factor in their extinction.
Further study in this direction may help us understand why animals go extinct and also help us protect and preserve them better. It may be premature to assume that all the extinct animals can be brought back. But, understanding the functionality and expression of those genes can help piece together the evolutionary puzzle. This experiment will allow us to study the genetic composition of extinct species at the very least.
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