Genetic Restraint

Things That Simply Should Not Be Done

This should not be done. I am not alone."¹ This was bioethicist Ruth Macklin's reaction to an announcement made earlier this year by a team of Chinese scientists to the effect that they had "edited" the DNA of human embryos in an effort to correct a genetic mutation that can cause thalassemia, a serious blood disease.

To edit the DNA, the team used CRISPR/Cas9, an enzyme complex. When injected into a cell, CRISPR/Cas9 acts like micro-scissors. It targets the defective section of DNA, snips it out, and replaces it with healthy DNA provided by the researcher. The technique is well established for editing adult human cells—for instance, to modify a patient's bone...