April 29, 2016 at 12:27AM

Tody I Learned: 1) ...a little bit about how praying mantises eat. Like a lion, it seems they like to go for the throat, ripping off their prey's head before munching down the body. Unlike a lion, they're surprisingly not that good at actually *killing* their prey. It can take quite a while for the mantis to chew all the way through. They don't seem particularly concerned about holding a creature a significant fraction of their own size still struggling to get away. They're really scarily effective at holding insects. 2) ...how to cut RNA with Cas9! It turns out Cas9 is perfectly happy cutting RNA as long as you provide a little DNA oligo containing the PAM that binds to the PAM site on the RNA. In other words, Cas9 only requires DNA at the PAM sequence, and only on one strand -- it doesn't particularly care what kind of nucleic acid it binds to and cuts past that (though to be fair, cleavage of RNA isn't nearly as efficient as cleavage of dsDNA (though it should *also* be noted that the Cas9 does *bind* quite well to RNAs -- it just doesn't cleave them quite as well once attached, it seems)). More here (Nature, sorry abuot the paywall): http://ift.tt/1rDQDZr 3) ...a circuit architecture for exact tracking of a target (up to a factor). Say you want to detect molecule A, and you want a readout that follows the concentration of A -- for instance, you might want to produce GFP proportional to the amount of some hormone in the cell. You can do that with species B and C and the following regulatory relationships: A (linearly) turns on production of B B (linearly) turns on production of C C very strongly competitively inhibits B, or otherwise stops it from activating A And that's it! For certain parameter choices, at least. It's pretty robust, but not perfectly so. Thanks to Niles Pearce on this one!