CRISPR/Cas: the gene scissors

In short: CRISPR/Cas is a tool that lets researchers cut and change the genetic material at a precisely chosen spot. It is simpler, faster and cheaper than older methods of genetic engineering.

In more detail: The system originally comes from bacteria, which use it to defend themselves against viruses. Emmanuelle Charpentier and Jennifer Doudna received the 2020 Nobel Prize in Chemistry for developing it into gene scissors.

In detail

• Natural origin: Bacteria store short pieces of viral DNA in their genome, the CRISPR sections, and recognise the same viruses when they attack again.
• The guide RNA: A short piece of RNA that matches the target DNA site leads the enzyme exactly there, much like an address.
• The cutting enzyme: The enzyme Cas9, the best known of several Cas enzymes, cuts through both strands of the DNA at the recognised spot.
• Repair by the cell: The cell repairs the cut itself; this often introduces small errors that switch a gene off, or a new section can be inserted deliberately using a supplied template.
• Research: In the laboratory, this makes it quick to test what a particular gene does by switching it off and observing the consequences.
• Medicine: The first therapies have now been approved in which blood stem cells are modified outside the body, for example to treat sickle cell disease.
• Agriculture: In plant breeding, CRISPR is used, for example, to improve resistance to diseases; how such plants should be regulated is being debated in many countries.
• Risks and ethics: The gene scissors can also cut at unintended places; changes to germline cells, which would be passed on to offspring, are banned in many countries and highly controversial internationally (stammzellen-und-gentechnik-grundlagen, dna-und-rna-unterschiede, bakterien-und-viren-unterschied).