CRISPR Revolution

CRISPR-Cas9 is a molecular tool borrowed from bacteria that edits DNA with surgical precision. Scientists program a guide RNA to match a specific DNA sequence, and the Cas9 protein cuts the double helix at exactly that spot. The cell's own repair machinery then fixes the cut, either disabling a gene or inserting new code.

The ethical stakes are high. Germline editing — changing DNA in embryos — would create permanent changes passed to future generations. Most countries ban it in humans, but the technology exists and the debate continues.