Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR) is a revolutionary gene editing technology that enables efficient, accurate genome modifications, in a large number of organisms and tissues. The procedure was first identified in a prokaryotic defense system, and consists of sections of genetic code that contain short repetitions of base sequences, followed by spacer DNA segments. Jennifer Doudna compares the simple corrective procedure to a word-processing software that allows someone to correct a typo in a hefty document. The ease and low cost with which the technology can be used, render the possibilities of its application endless.
The process works to edit genes by capturing a short nucleic acid sequence from an invading pathogen, which is then integrated into the CRISPR loci amongst the repeats. This causes small RNA to be reduced by the loci, which can then be used to guide a set of end nucleuses to resist the attacks of invading pathogens in the future. There is ongoing research into using the technology to treat diseases such as cancer, sickle cell anemia and some forms of blindness. The possibility has also be raised that CRISPR can be used as a cure for Duchenne muscular dystrophy, and The Salk Institute is researching ways in which they can modify it to produce a pig with transplantable human organs.
They are not the only ones that believe that the technology will work well on animals, as Chinese scientists have already used it to delete genes that inhibit muscle and hair growth in goats. This has allowed for the expansion of the country’s meat and wool industries. There is also a team researching ways in which CRISPR can boost agricultural output, by creating super plants. These plants will be modified to resist fungi, and other things that may restrict their growth.
Cas9 is one of several restriction nucleuses that enables the editing of genes using CRISPR. It works as a molecular scissors, and uses a synthetic guide RNA to introduce a double strand break at a specific location on a DNA strand. This gRNA directs the cut through hybridization with its matching genomic sequence. During each procedure, a DNA construct with three major components: the Cas9 enzyme, gRNA and the replacement DNA template; is injected into an organism to modify its genes.
After the procedure has been applied and the cell attempts to repair the break, there is the possibility of added genetic modifications or an error occurring. Modified Cas9 versions prevent this from happening as they introduce single-strand nicks to the DNA, which pair up to stimulate the repair mechanism. Scientists agree that the CRISPR method is easy to use, but comes with huge moral responsibilities as it has the power to change the way in which humans, and other organisms, evolve. As the technology is applied in more experiments, possible immoral actions will need to be avoided.