“The Gene Hackers,” by Michael Specter. The New Yorker, 11/16/2015.
A new technology is revolutionizing DNA modification by making the process hundreds of times easier, in some cases reducing the time required from months to seconds. Its acronym is CRISPR, Clustered Regularly Interspersed Short Palindromic Repeats. (Phew, that was hard just to copy. A palindromic repeat is something that is the same forward or backward, like “1881.” This is the first time I have seen the word outside of a crossword puzzle.)
CRISPRs are clusters of DNA sequences discovered in bacteria that can recognize invading viruses, deploy an enzyme to chop them up, and use the pieces to form a rudimentary immune system. (Viruses are essentially free-floating strands of DNA.)
Researchers have found ways to use this same process to insert DNA segments anywhere into any gene or to simply cut out objectionable parts. CRISPRs have two components: one is the enzyme that cuts the DNA like a knife and the other is a strand of RNA that leads the knife past thousands of sections to the right place to cut and insert genetic information from the RNA. “This was a finding of mind-boggling importance. And it set off a cascade of experiments that have transformed genetic research,” said one scientist. Commercial companies already synthesize almost any of the needed components, and researchers can order whatever they want online for delivery in a day or two.
Working mostly with mice, researchers have corrected genetic errors responsible for sickle-cell anemia, muscular dystrophy, and the defect associated with cystic fibrosis. In agriculture, a Chinese group of scientists have modified wheat by removing a gene that makes it susceptible to powdery mildew, one of the world’s most pervasive blights. Since genetic material is only removed and no foreign DNA is introduced, they hope the wheat products will be acceptable to the public.
Myopia (nearsightedness) is caused by a common mutation in our genes that would have died out over the generations by natural selection, but we have invented glasses that have made it only a nuisance. Instead of starving in a jungle full of food we can’t see, myoptics, like me, go right on reproducing, and myopia is still with us.
A modification to DNA, natural or synthetic, has always taken years to spread through the population. CRISPRs changes that, too. Normally, a gene only has a 50% chance of being transmitted by sexual reproduction, but a CRISPR mutation can be made to copy itself in every generation without fail. This is often desired. Not only could our myopia be halted, but also all of our descendants made free of myopia.
The specter of a future dystopian world full of manufactured humans is repugnant, but modification of human DNA is bound to begin. The advantages are too important to ignore. “It’s going to happen,” says one scientist. The technology is moving far more quickly than the ethical considerations can keep up.