From the hundred and thousands of years it takes for natural selection to change the genetic makeup of an organism, the winners of this year’s Nobel Prize for Chemistry brought it down to just a few hours. The biochemist duo Emmanuelle Charpentier and Jennifer Doudna were named for the prize for developing the revolutionary tool CRISPR/Cas9 genetic scissors in 2012.
Adapted from the naturally occurring DNA-editing tool in the immune system of a bacteria, this “scissor” can be used to edit precise sections of the DNA.
“There is enormous power in this genetic tool, which affects us all. It has not only revolutionised basic science, but also resulted in innovative crops and will lead to ground-breaking new medical treatments,” says Claes Gustafsson, chair of the Nobel Committee for Chemistry.
In the 111 occasions that the Nobel Prize for Chemistry has been awarded since 1901, this is the first time two women have shared it. Till now, only five women had received the award, including Marie Curie in 1911 and her daughter Irène Joliot-Curie in 1935.
French microbiologist and biochemist Charpentier, currently the director of the Max Planck Institute for Infection Biology in Berlin, was interested in the research of pathogenic bacteria, particularly one that causes life-threatening complications such as sepsis (blood infection) and soft tissue breakdown in humans called Streptococcus pyogenes.
On the other hand, America biochemist Doudna was fascinated with Ribonucleic Acid or RNA that plays a in coding, decoding, regulating and expression of the genes. She was studying the exciting new role of RNA in regulating gene expression, when she stumbled upon CRISPR or clustered regularly interspaced short palindromic repeats.
CRISPR is essentially a sequence that is repeated over and over again between unique sequences in the genetic material of various bacteria. What Doudna found was that the CRISPR associated genes (Cas) were similar to proteins that specialise in unwinding and cutting up DNA.
At the same time, Charpentier’s study of the S. pyogenes found another piece of the puzzle – a previously unknown small RNA molecule called tracrRNA that exists in large amounts in the bacterium. Careful analysis of the genetic codes reveals that it indeed it is a part of the bacteria’s repetitive CRISPR system.
A collaboration between the two researchers led to the understanding that the Cas9 is the scissor that cuts off the DNA molecule whereas the CRISPR was necessary to recognise where the cuts have to be made. In their natural form, the scissors recognise DNA from viruses, but Charpentier and Doudna proved that by changing the CRISPR part of the scissors to match the code where the cuts are to be made, any DNA could be edited at exactly the right places.
Since their discovery, it has become extremely easy for scientists to play with the DNA of organisms to study their effect on the physical form. Apart from basic research, it has also helped in developing crops that can withstand moulds, pests and drought. It is also being used in the field of medicine to find ways to cure cancer and other inherited diseases.
Theoretically, the technology makes it possible to select certain traits in off-springs by editing their genomes. But, globally scientists agree that germline editing or editing of traits that can be passed on to the next generation is irresponsible without data on the safety of the procedure.
However, a controversy blew in November 2018 up when a Chinese scientist He Jiankui edited the embroyo of twins to delete a gene that makes them susceptible to HIV.