A book, and then the movie, Jurassic Park revolved around a very intriguing plot. An entrepreneur joins forces with a group of scientists to bring dinosaurs like Tyrannosaurus rex back to life. Their strategy is incredible; Dinosaur DNA is isolated from the gut of a blood sucking insect preserved in amber, which had gotten stuck in tree sap tens of millions of years ago. This sap fossilized into amber thus preserving the insect and along with it the dino blood. The DNA was then amplified through the Polymerase Chain Reaction (PCR) and used for cloning extinct dinosaurs.
Was the movie right, can we really bring dinosaurs back on the planet or is this just a fantasy? It may seem plausible to a layman, but a closer look reveals that it’s not so easy. Firstly, the traditional limit of the most efficient PCR is around 40 kilo base pairs (kb); nowadays this limit has increased to a few hundred kilo base pairs. This means that a PCR cannot amplify more than a few hundred kb of DNA fragment. How long do you think the size of a dinosaur genome might be? Guess what? It’s unimaginably larger than a few hundred kb!
So we might be able to amplify a protein of a dinosaur but not enough to bring it back on its feet, alive and roaring. This is of course assuming that we have already sequenced the genome. DNA is fragile; it can’t last for long. DNA has limited chemical stability and decays without the enzymatic repair mechanisms of living cells. In tropical environment under normal conditions it starts degrading immediately due to nucleases and bacterial activity, Under optimum conditions this process slows down and DNA can survive on average for about 10,000 years , occasionally under subzero temperatures this can be 100,000 years or so. Examples for this have been retrieved from Arctic permafrost (so now you can imagine the cold). Therefore, we can’t find its complete genome anywhere. Furthermore, there is no proof that one mosquito sucked blood from a single dinosaur, or multiple dinosaurs, or even different species altogether! Possibilities are, it fed on several species, making it extremely difficult to obtain a pure DNA sample. Even more so due to genetic contamination from the mosquito and it’s gut microbiota!
This isn’t a new topic. Few weeks before The Jurassic Park hit cinemas, a study was published in Nature that a 120-135 million year old weevil, trapped in Lebanese amber, was sequenced for some of its genome. But in this case, modern day weevil had already been sequenced and its primers were used for sequencing its prehistoric ancestor. Birds are the closest living relatives to some dinosaurs, so by stretch of imagination it can be assumed that their primers can be adapted for dinosaur DNA.
Several attempts are being made to bring back extinct species ‘The Long Foundation’ has initiated a project called ‘Revive and Restore’ which aims at bringing back lost species like the woolly mammoth, passenger pigeon and the Thylacine (Tasmanian Tiger).‘de-extinction’, aims at reversing extinction in the emerging field of conservation genomics. Again, the issue about the difficulty of obtaining uncontaminated samples and sequencing their whole extinct genomes is raised.
Even though all of this might portray a bleak picture, the solution may lie in advanced bioinformatics and molecular techniques used in ‘synthetic biology’ might be able to isolate, identify and patch up, successfully isolated sequences into the genome of the extinct animals’ closest living relatives. For the passenger pigeon, it would be the band-tailed pigeon for instance, and for the woolly mammoth, the Asian elephant. Other animals like the great auk, the ivory-billed woodpecker and the Caribbean monk seal, among others could be brought back to life using this technique. Dinosaurs may follow using chicken or ostrich primers and base DNA, with ostrich eggs being used for cloning and hatching.
Synthetic biology promises to save the day. It is an emerging amalgamation of various fields of biology, engineering and computational techniques. Its potential applications span diverse areas, from medicine to food technology, from environment to renewable energy, and even beyond. Synthetic biology holds the solutions for many of our problems and the good news is that it is also emerging in Pakistan! Quite recently, a team of selected students are taking their project to the international synthetic biology centric competition, iGEM, taking place these days from 27th to 31st of October in USA. The team which has been selected from all over Pakistan and trained by iGEM Peshawar, is using biology to counter one of Pakistan’s most common environmental problems. Can you guess what it is? Find out in our next article. Stay tuned!
Length of DNA in PCR
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Gutiérrez, G., & Marin, A. (1998). The most ancient DNA recovered from an amber-preserved specimen may not be as ancient as it seems. Molecular biology and evolution, 15(7), 926-929.
Redford, K. H., Adams, W., & Mace, G. M. (2013). Synthetic biology and conservation of nature: wicked problems and wicked solutions. PLoS Biol, 11(4), e1001530.
Wellhausen, R., & Oye, K. A. (2007, October). Intellectual Property and the Commons in Synthetic Biology: Strategies to Facilitate an Emerging Technology. In 2007 Atlanta Conference on Science, Technology and Innovation Policy (pp. 1-2). IEEE.