CRISPR

CRISPR is short for clustered regularly interspaced short palindromic repeats, which describes a pattern in bacterial DNA rather than anything a reader needs to picture. The US National Human Genome Research Institute defines it as a technology that research scientists use to selectively modify the DNA of living organisms, and notes that it was adapted for use in the laboratory from naturally occurring genome editing systems found in bacteria.

The natural version is a defence. Bacteria keep fragments of viruses that attacked them, and use those stored fragments to recognise the same virus later and cut its DNA. The laboratory version borrows the cutting machinery and aims it deliberately. In the common form, a guide molecule is written to match the sequence a researcher wants to change, and a protein called Cas9 makes a break in the DNA at that point. The cell then repairs the break, and the repair is what alters the gene.

The word selectively is the important one. Older techniques could add genetic material but not choose the location precisely, which is the difference CRISPR made. It is one technique among several used in gene therapy rather than a synonym for it, and being able to edit a sequence is not the same as knowing which sequence to edit, which remains the harder problem for most diseases.