The cell cycle coordinates growth, DNA replication, and division through changing regulatory signals. In the engineered yeast used for optovolution, continued proliferation depends on a protein producing the right output at the right stages. This makes the cycle a recurring selection test for protein dynamics, without implying that every cell must divide continuously to remain alive.
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15:23Harmonic in that like there's I think I think it just comes from like harmonies and the fact that it's you can fit it with a sine wave. Mhm. >> And an oscillator, I think it just means it's oscillating from one state to another state, >> right? And so the cell cycle is an innate biological oscillator because it's oscillating from growth to division to growth to division. Right. So it's a cycle. >> There's a cycle that has some kind of period. >> Yes. >> Um and a starting position and an ending position >> and then it goes back to >> and it go and and it repeat there's a repetition of the movement between those two. >> Exactly. Yeah. Yeah. And so, and so what we want to do here is in order to create
16:03an oscilly protein, something that can toggle between an on and an off, I'm going to couple it, connect it somehow to the original oscillator of biology, which is the cell cycle. And would the potential benefit of doing something like that be the biology? It's it's sort of like the same reason we use um um was it quazars for clocks >> uh because it oscillates rhythm on a on a cycle that is so consistent and so repet like it's a dependable system to base off of. >> Yeah. With a quazar, it's like so far away that it doesn't depend on my position the the earth's position around
16:45the sun and so on. So, it's always in the same spot in the sky, right? And so, it doesn't depend if I'm in July or March, the quazar is always there. And so, I can use that as my clock to figure out how long my day is. In in this sense here, we're using the cell cycle because it's the cell cycle is just going to go, right? Otherwise, the cell dies, >> right? So if I can make a protein that I need to be dynamic tied to the cell cycle, then if the protein arrests into either an only on or an only off state, it's going to kill the cell. >> Mhm. >> And then that protein is not going to proliferate in evolution. That's the sort of high picture idea of how we're
17:25going to use evolution here in this case, right? Because now it's survival of the fittest. But in order to be fit, I need to be able to toggle the internal dynamics. >> The protein needs to be able to go from one state to the other. >> Mhm. >> Right. That's what's key. >> So, let's talk about this biological oscillator that I've been going on about. This is the ukareotic cell cycle. Okay. Mitosis, >> which is something that I hope everybody who did high school biology knows about the idea of binary fishision, right? The cell doubles its DNA and then it splits in two. and then it doubles its DNA and then it splits in two. Well, the doubling of that DNA happens during interphase, specifically the Sphase. That's the synthesis phase. The
18:07splitting in two is the mitosis part. But after splitting in two, now each of these daughter cells have only one >> copy of DNA. In order to replicate again, they need to go through the Sphase again. They need to synthesize the DNA and double their DNA and then split up again. Now this entire cell cycle is driven by something called cycl dependent kinases CDKs. Okay, these cycl
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