Molecular Scissors

Genetic engineering is not new—the capability to manipulate human DNA, and the associated ethical concerns, have been around since the 1970s. However, within the past five years, an effective and affordable new tool for precise gene editing, called CRISPR, has fanned the fires of hope, curiosity, and controversy for both scientists and the public, bringing discussions about genetic engineering back into the spotlight.

CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. It is a naturally occurring genetic feature of bacteria used to fight invading viruses. Adapted by scientists for laboratory use as a molecular biology tool, CRISPR has greatly reduced the time and cost associated with gene editing in a broad range of organisms. CRISPR gives researchers the ability to more easily add, remove, or change regions of an organism’s DNA, which has potential applications for agriculture and for the study and treatment of disease.

CRISPR was discovered by scientists in Spain in 1993, but its function and capabilities were not understood for another ten years. It was not until 2013 that the first results demonstrating its use for mammalian gene editing were published. With that landmark paper, however, interest from the research community and the private sector exploded. CRISPR is now transforming how scientists perform experiments with gene splicing and how they envision the future of CRISPR for potential medical and agricultural applications.

Similar to some other gene editing tools, CRISPR works like a pair of molecular scissors. It cuts DNA at specific locations and either deletes sections or replaces them with alternate sequences. CRISPR involves two key biochemical pieces: first, a short stretch of RNA—a molecule similar to DNA—that binds to the target DNA sequence, acting as a guide for the CRISPR system, and second, an enzyme (a type of protein) that does the cutting. The RNA sequence is fairly simple to synthesize in the lab. This makes the CRISPR process easier than some of the older gene editing systems that require the complex bioengineering of desired molecules. The most common enzyme used in CRISPR is called Cas9, though there are other enzymes that work in nature and are also used in the lab. But because Cas9 is the most commonly used enzyme, the whole gene editing system is sometimes referred to as CRISPR-Cas9.

Media sources abound with stories about the possible use of CRISPR for human gene editing. Most current work, however, is in fundamental laboratory science—studying cells and animal models whose genes have been altered using CRISPR. Such studies of genetically altered animals, using myriad techniques and tools, have been done for decades to model human health and disease. This field of research provides important information about how certain genes influence the human body’s function and well-being. It can be particularly powerful in studying disorders that are linked to the malfunction of genes.

National Geographic