Researchers at Mie University in Japan have successfully used CRISPR-Cas9 technology to remove the extra chromosome responsible for Down syndrome in lab-grown human cells, marking the first instance of deleting an entire human chromosome with gene editing. This allele-specific editing targeted only the supernumerary chromosome 21, which causes the disorder affecting 1 in every 700 births. Post-editing, cells exhibited normalized growth and activity patterns, with genes linked to brain development upregulated and inflammation-associated genes downregulated. While the innovation opens potential pathways for future therapies, the approach raises significant ethical considerations regarding its clinical application.