CRISPR Explained: Editing the Code of Life

CRISPR-Cas9 has been called molecular scissors — a tool that lets scientists cut DNA at a precise location and rewrite the instructions of life. In just over a decade it has transformed biology.

Borrowed from bacteria

CRISPR is not a human invention. Bacteria evolved it as an immune system, storing snippets of viral DNA to recognise and destroy invaders. Researchers realised this targeting system could be reprogrammed.

How an edit is made

• A guide RNA is designed to match the target DNA sequence.
• The Cas9 protein follows the guide and cuts both DNA strands.
• The cell's repair machinery stitches the break — disabling or replacing a gene.

“We can now write to the genome almost as easily as we once learned to read it.”

— Nature Biotechnology

The promise is enormous — from curing inherited blood disorders to engineering drought-resistant crops. But so are the questions of ethics and access, which society is only beginning to answer.