Let’s face it: as Year 12s, most of our daily existential dread is confined to the UCAS personal statement and EPQ if you are doing it of course, or wondering if the cafeteria will run out of paninis before you get let out of lessons 5 minutes too late. But recently, Columbia University scientists decided to elevate global existential dread by publishing a preprint study that asks a much heavier question: Are we finally ready to safely rewrite the genetic code of human embryos?
According to a recent piece in New Scientist, we might be closer than you think.
For years, the gold standard of genetic engineering has been CRISPR-Cas9. You may have heard of it in the news; it’s usually described as a pair of “molecular scissors.” In past embryonic experiments, CRISPR had a terrifying habit of introducing massive chromosomal abnormalities. It was less “fine-tuning a masterpiece” and more “taking a weed-whacker to the human genome.”
A new study led by biologist Dieter Egli showed that the team bypassed traditional CRISPR in favor of a newer, much trendier technique called base editing.
Instead of hacking through the DNA double helix and leaving the cell to desperately glue itself back together, base editing works like a chemical pencil eraser. It targets a single “letter” of the genetic code – changing a Cytosine to a Thymine, or an Adenine to a Guanine, without actually breaking the DNA strand.
Egli’s team targeted genes responsible for high cholesterol (PCSK9) and blood disorders like sickle cell anaemia. The results? No major chromosomal destruction. It was efficient, precise, and arguably the most elegant genetic edit performed on human embryos to date.
So, is it safe? Can we pack our bags and head to the nearest designer baby boutique?
Not exactly.
The study hit a pretty massive snag that geneticists call mosaicism. While the base editors were highly effective, they didn’t always catch every single cell in the early-stage embryo. In fact, 80% of the embryos turned out to be genetic mosaics.
Let’s use an analogy (another shoutout to Mrs East who is a pro at them). Imagine trying to repaint a house, but your brush only hits four out of every five bricks. You end up with a patchy, multi-colored mess. In biological terms, if these embryos were allowed to develop into actual human beings, they would grow up with a mix of corrected cells and uncorrected, disease-carrying cells. It’s hard to claim you’ve “cured” a hereditary illness if 20% of the patient’s body missed the memo.
Beyond the technical glitches, we have to talk about the massive elephant in the laboratory: ethics. Right now, the scientists and commercial backers involved in this research argue that base editing is just a superior alternative to discarding faulty embryos during IVF. If a couple has a genetic mutation, you just “fix” the embryo instead of throwing it away. Sounds noble, right?
But the line between medical therapy and cosmetic enhancement is notoriously blurry. One of the startups backing the Columbia research already offers embryo screening for traits like height and estimated IQ. It doesn’t take a genius to see where this goes. If we master the ability to safely rewrite the code, how long before “preventing heart disease” turns into “making sure my kid is tall enough to play in the NBA and smart enough to win the next noble prize”?
Furthermore, critics rightly point out that we already have safe reproductive technologies (like Pre-implantation Genetic Diagnosis) that allow parents to screen and select healthy embryos without interfering with their DNA structure.
So, to answer the question: Are we getting to the point where it’s safe? Scientifically, there have been incredible advancements in the precision of this technology however, until someone solves the 80% mosaicism problem, gene-editing human embryos remains a high-stakes gamble. For now, the technology is strictly illegal for reproductive use in the UK, the US, and most of the developed world.
