What is CRISPR?
When it comes to the latest breeding technology, many of us have probably heard of the acronym CRISPR, one of the better-known tools in the world of genome editing. CRISPR-Cas, which stands for Clustered Regularly Interspaced Short Palindromic Repeats and its associated protein called Cas, work together like a pair of molecular scissors to directly edit the native genomes of various organisms, plants, animals, and even humans, in a very precise and predictable manner. The efficiency and precision of CRISPR-Cas tools are enabling scientists to accelerate the breeding process by allowing desired characteristics and improvements to be achieved in a fraction of the time normally required with conventional breeding practices. The versatility of its use and widespread applications suggests that the technology is poised to deliver solutions to feed the world, protect the planet and mitigate climate change. But let us take a step back and look at the origins of the CRISPR-Cas discovery.
Learning from Nature
The discovery of CRISPR dates back to the turn of the century when scientists recognised that CRISPR forms part of the natural defence system that bacteria use to fight invading viruses.
How does it do this? When viruses attack bacteria, they take over their hosts by injecting their DNA into bacterial cells. The bacteria respond by incorporating small segments of DNA from the invading virus into its own genome. These viral DNA segments are what is known as CRISPR and is used as an early warning system to protect bacteria from future attacks by the same virus. When viral infections re-occur, the CRISPR segments identify and flag the matching DNA of the invading virus, which triggers its associated Cas9 enzyme into action, to splice up the viral DNA and disable the virus.
By gaining an understanding of how CRISPR works in nature, scientists were quickly able to adapt and improve the science of CRISPR-Cas technology to target and edit DNA at precise locations in the genomes of a whole host of different organisms. In October 2020, Emmanuelle Charpentier and Jennifer Doudna were awarded the Nobel Prize in Chemistry for their ground-breaking work on developing CRISPR into a gene editing tool.
Utilising CRISPR as a gene editing tool
The rapid advancement of CRISPR-Cas breeding tools over the last decade has been catalysed by our improved understanding of DNA, the ability to sequence entire genomes of organisms and also knowing more about how specific genes function to express specific traits.
As a modern-day breeding tool, the CRISPR-Cas9 technology functions as a two-component system. The CRISPR component works like a homing device that guides the associated Cas9 scissors to snip the DNA at targeted sites, thus allowing deletions, edits, or additions to be made at specific sites within the organism’s genome with the help of the cell’s own DNA repair system that is tasked with fixing errors or breaks in the DNA strand. But as often happens in science, it continues to evolve and already there are newer adaptations of CRISPR available that do not involve cutting DNA, but instead are able to turn genes on or off. Other versions include “base editors,” that are able to change one letter of the DNA code to another, without cutting DNA.
By directly altering the genetics of organisms, CRISPR tools are able to increase the genetic diversity of species, which in turn provides more genetic variation for traditional breeders to work with, thereby speeding up the breeding process. Long before CRISPR arrived, various other modern breeding tools were deployed to edit the genes of some plants and animals, but the drawback of these tools is that it was extremely expensive, cumbersome, concentrated on improvements in a limited number of traits and crops and required more years to successfully accomplish desired trait improvements. The major advantage of CRISPR technology over earlier breeding tools, is the ability to facilitate genetic improvements in a precise, less expensive, flexible, and easier to use system that is grounded in the science of nature. Another distinguishing benefit of CRISPR tools, is that many of the technology applications exclude the transfer of “foreign DNA” and instead result in products that are indistinguishable from similar products developed through traditional breeding methods or obtained through ubiquitous mutations that occur in nature.The full article is for subscribed members only. To view the full article please subscribe. It’s FREE!Log In Register
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