CRISPR/Cas9 is a DNA cutting system that allows scientists
to harness the power of natural DNA repair mechanisms,
giving them the potential to cure genetic disease.
The heart of this amazing technology is the Cas9 protein
which can cut DNA at a specific site
using the enzyme component selected to target a specific location in the genome.
The Cas9 protein scans the DNA
and pauses its certain sequences called PAMs.
Cas9 then opens the DNA strands to determine weather the DNA matches its RNA component.
A natural repair complex recognizes the cut DNA and forms a donut-like shape near the ends.
This protein complex then attracts the cell’s processors for repairing the cut.
This complex can attract a protein that adds bases at the break site.
Alternatively, the donut-shape complex can attract an enzyme that removes part of the DNA.
Both deletion and insertion scenarios result in gene inactivation,
which is useful when the gene contributes to disease.
A CRISPR/Cas9 infused DNA cut
can also engage a different natural cell process called homology directed repair
which can repair a disease causing gene defect.
After the CRISPR/Cas9 system creates a DNA cut, enzymes that remove bases can reach the cut before the donut-shape complex is formed.
When DNA containing the correct information is provided, the cell’s repair machinery can use this DNA to repair one of the strands.
The second strand will then be repaired using the corrected strand as its template.
This repair process introduces the site specific and precise DNA sequence that was encoded on the single strand template.