The citizens of Singapore have only four days to decide how they feel about “three-parent babies” — children whose normal, two-parent DNA is modified to include genes from a third person in order to potentially thwart life-altering genetic disease.

On June 15, a Bioethics Advisory Committee, headed by Oi Lian Kon, Ph.D. of the National University of Singapore, will officially stop accepting comments from the public and other religious groups about a procedure called mitochondrial replacement therapy (MRT). MRT is a type of genome manipulation in which a tiny subsection of DNA that’s sequestered away from the rest of the cell’s main stock is replaced by that of a third-party donor. Doing this, researchers say, can prevent certain conditions like strokes and epilepsy. This procedure, unsurprisingly, has generated controversy in the past. Settling the ethical debate will require deciding whether MRT actually qualifies as “genetic engineering.”

singapore genetic engineering
The National University of Singapore is playing a key role in their decision on whether to legalize MRT.

The controversy surrounding this procedure rests on some important biological distinctions. The mitochondria from which MTR derives the third-party DNA is a small organelle within cells that has its own, separate DNA. (It makes up only 0.000005 percent of all DNA.) Sometimes, this mitochondrial DNA (mtDNA) carries dangerous mitochondrial diseases. So, in MTR, mtDNA from a healthy “third parent” is inserted into the mitochondria of an embryo at risk of developing these diseases. But in MTR, the mtDNA itself isn’t destroyed or manipulated; rather, the whole mitochondria is just swapped out.

In a TODAY interview published Monday, Kon said that MTR “doesn’t come under the sphere of ‘engineering.’ It would be like an individual who has a kidney transplanted from a donor.” The first country to legalize MRT, the UK, used the same distinction — swapping mtDNA versus “editing” DNA itself — to draw a line in the sand. “[The] use of MRT to produce male offspring — what the NAS recommended as a first step — ‘would not constitute genetic or germline modification,’” noted a 2016 report in the Journal of Law and the Biosciences. The United States’ standing policy on MRT, outlined in a 2014 report from the Cellular, Tissue, and Gene Therapies Advisory Committee (CGTAC), takes a similar line, calling MRT a “very different type of genetic change.” The US, however, is still performing “clinical investigations.”

The real issue when it comes to MRT lies in the difference between “replacing” and “editing,” to use the FDA’s words. Editing the genomes of children, some researchers argue, can have serious ethical ramifications, as anyone who’s seen Gattaca has likely realized. “Replacing” DNA, so far, has been the path to legality for MRT, as demonstrated by the UK’s actions.

If Singapore succeeds, proponents of MRT can put another W in the “replacing” column.