Ever since James Watson and Francis Crick revealed the molecular structure of DNA, the prospect of tweaking the building blocks of life in order to alter biology and cure diseases has enthralled researchers and science-fiction writers alike. In the seven decades since then, genetic technologies have blown open our scientific horizons, paving the way for major breakthroughs in biological sciences, healthcare, and archaeology – and we’re just getting started.
Bringing Extinct Species Back From The Dead
It might sound like a plot from a Michael Crichton novel, but researchers are actually using genetic tools to try and bring certain species back from extinction. Led by geneticist Dr George Church, a Harvard-based team is currently working on resurrecting the woolly mammoth by altering cells from the ancient behemoth’s closest living relative, the Asian elephant.
Given that the two species share 99.96 percent of their DNA, this ambitious project really only requires the alteration of a few thousand elephant genes in order to reintroduce mammoth-like traits. This can be achieved thanks to a technique called CRISPR, which uses ribonucleic acid (RNA) in order to guide a protein called Cas-9 towards a specific section of DNA, where it then cuts the two strands of the double helix so that new genetic material can be inserted.
Similar projects are currently underway in order to try and bring back the extinct passenger pigeon and the Tasmanian tiger, although no actual animals have been created so far. Instead, researchers are simply growing stem cell-derived tissues that express certain characteristics pertaining to these long-lost species. For example, Church and his colleagues have been altering the DNA of elephant stem cells in order to create red blood cells that can function at sub-zero temperatures, just like those of their mammoth predecessors.
Once they have succeeded at growing blood, fat, hair and other tissues that sufficiently resemble the woolly mammoth, the team will then attempt to create an embryo that could give rise to an elephant-mammoth hybrid. If successful, then not only will this approach enable us to protect certain endangered species from extinction, but it could also play a role in the fight against climate change. Indeed, the reintroduction of giant herbivores like the woolly mammoth to the Arctic is likely to encourage the growth of steppe grasses, which reflect sunlight back into space and therefore cool the region. This, in turn, could slow the melting of the permafrost and prevent the release of huge amounts of carbon trapped within it.
Back to the living, and numerous CRISPR-based medical procedures are now being developed in order to create cures for a range of diseases. For example, researchers at the University of Pennsylvania are currently conducting a clinical trial to see if the gene-editing tool can be used to treat cancer.
By altering the DNA of patients’ immune cells, the team hopes to boost these cells’ ability to hunt down and destroy cancer cells. Once these are reintroduced into patients’ bodies they should be able to eliminate tumors, which would revolutionize cancer treatment in the future.
Similarly, scientists hope to use CRISPR to cure HIV, with trials already having been conducted to see if the technology can eliminate the virus by damaging a gene called CCR5, which pathogen requires in order to invade cells inside the body. Initial tests have shown that the procedure is safe, and researchers are now working on improving its efficacy.
Genetic tools may be taking us into an exciting new future, but they can also help us look back into the past and uncover the secrets of our origins. Ancestry tests, which reveal the geographical lineage written into an individual’s DNA, have become hugely popular in recent years, and are made possible thanks to a process called polymerase chain reaction (PCR).
Sometimes referred to as ‘genetic photocopying’, this method allows scientists to amplify small sections of DNA by replicating it billions of times in order to detect and study certain genes. The process begins with the denaturation of the DNA double helix into single strands under high temperature, before an enzyme called Taq polymerase assembles the relevant nucleotides in order to rebuild each of these into a new double helix.
By repeating the procedure up to 30 times, huge numbers of copies of a given stretch of DNA can be created, which is useful for diagnosing genetic diseases and for genetic profiling. Famously, the technique was used to study the DNA of a 42,000-year-old skeleton in Australia known as Mungo Man, and revealed that this ancient antipodean possessed certain genetic traits that are exclusive to modern Aboriginals, thereby confirming their status as the first Australians.
Unfortunately, however, it took more than a decade to decipher these results as researchers conducting the original study in 2001 accidentally contaminated their Mungo Man sample, meaning they unwittingly ended up conducting PCR on their own DNA.
In Jurassic Park, geneticists extract DNA from an ancient mosquito in order to resurrect the dinosaurs on which the insect had feasted. While that’s obviously not likely to happen in real life, scientists in Japan say that it may be possible to identify criminals by analyzing blood from mosquitos found near a crime scene.
To prove their theory, the researchers asked volunteers to allow themselves to be bitten by mosquitos, before extracting DNA from the insects and analyzing it using PCR. While the scientists were able to successfully identify each study participant from the samples they retrieved, it’s unlikely that this kind of evidence would ever stand up in court, given that mosquitos tend to bite innocent bystanders as well as criminals.