Put them together, and they create a tool you can use to tweak an organism’s genome. To do this, CRISPR searches the organism’s DNA for a certain sequence-specifically, the one encoded by the guide RNA, which holds the inverse sequence of your target DNA.
“Cas9 opens up the DNA, it separates the strands of the double helix in a very small area, and allows the guide RNA to pair with one of the strands,” explains Dana Carroll, a professor of biochemistry at the University of Utah. If it is not a good match, Cas9 and guide RNA fall off and try again somewhere else.” When it finds the right sequence, the Cas9 protein slices the DNA at that precise spot.Īt this point, if you leave the cell alone, it will usually mend CRISPR’s cut-but it will occasionally also make a mistake in the repair process, breaking a gene or other parts of the genome.
Since CRISPR repeatedly goes back and slices the DNA again after the cell mends it, the gene eventually breaks, or, in technical terms, gets knocked out. And, if you add new DNA, the cell may incorporate it while fixing the cut. This means you can insert DNA where you want to in the genome-you just need to know the organism’s genetic sequence of your desired target area. The idea behind the kit experiment is quite simple. coli so that it can grow on an antibiotic called streptomycin, which normally kills bacteria. With materials and instructions from the kit, I will introduce CRISPR into the bacteria cells, and use it to rewrite a tiny part of their DNA, creating genetically altered cells that happily thrive on streptomycin.
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