Japanese researchers led by Dr. Ryotaro Hashizume successfully used CRISPR-Cas9 to remove the extra chromosome 21 responsible for Down syndrome in lab-grown human stem and skin cells. Allele-specific editing targeted only the trisomic chromosome, enabling edited cells to normalize behavior, grow faster, and reposition gene expression to reduce inflammation and abnormal metabolism. This groundbreaking work is the first demonstration of CRISPR erasing an entire chromosome, enhancing understanding of trisomy pathology and opening new prospects for therapeutic research, amidst ongoing ethical discussions.