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Say hello to biggest little thing in biotechnology!
This is a stylized model of a guide RNA from the CRISPR/Cas system bound to its target DNA. If you haven't heard of CRISPR/Cas9, see the protein model's page. To many biologists, CRISPR symbolizes a revolution that is happening right now in the way we study life. Borrowed from bacteria, this RNA/protein toolkit can be used to make targeted "edits" to the genomes of anything with DNA. This pendant is designed to show how the targeted DNA and the guide RNA fold inside a Cas9 protein . The PAM motif of the DNA is attached to the bail; this is the sequence that a cas9 protein can recognize and pry apart to compare with the RNA sequence it's carrying. Just after the PAM motif, one strand of the DNA is flipped 180 degrees, and if its sequence matches the guide RNA (the folded-up structure on the bottom half of the pendant), cas9 cuts the DNA in two places. In this model you can see the two cuts: both the paired and unpaired strand are cut 3 nucleotides away from the PAM motif, making a double-stranded break. When DNA breaks, the cell will try to repair it, but mistakes often get made that produce a mutation at the site of the break. The magic of this system is that we can design the guide RNA to target basically any sequence! So if you're curious about how any particular gene works, you can use CRISPR to modify it in different ways and observe the consequences.
I styled this model so it can slip onto a necklace chain. If you're interested in something that will sit on a flat surface, this design is also available without the bail. If you prefer 3D, I made mini and megascale models of the actual crystal structure cited below. And if you want to go all out, check out the mini or mega models of the entire protein/RNA/DNA complex!
 Hiroshi Nishimasu et al., "Crystal structure of Staphylococcus aureus Cas9." Cell (2015)