Clb5 is a cyclin involved in initiating DNA replication, and its activity must be controlled over the cell cycle. The optovolution system exploits the contrast between needing cyclin activity at one stage and being harmed by inappropriate persistence at another. A protein that regulates this signal must therefore do more than remain permanently active.
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18:31dependent kinases are formed and degraded at very specific times. And if we go back to to photo 11, what we'll see is what's happening is a certain compound comes up during let's say the G1 phase, which is the very beginning of interphase. So this is right after mitosis, right after the split, a certain cycl E shows up in the cell. Okay? And that's going to trigger the next phase. Okay? Then during the Sphase, during synthesis, another cycl comes up. That's going to trigger the next phase. Now, how is that triggering happening? The triggering is happening because the certain cycl shows up and it immediately gets degraded. So it's only
19:13there for a short amount of time. So it's like this boop signal, you know, it doesn't stick around. It's it's maybe like um is an analogy. It's it it's like the ignition when you're starting your grill and you click the button on the grill to get the ignition going >> and it's only there at the beginning but then the fire's going and it's not there. >> Yeah. Yeah. Exactly. And we don't want the you know the the whole time, right? You want it to just sort of start and it starts the phase and then it keeps going. And how does the cell regulate that? Well, the cyclones show up as molecules and then they get degraded. So they're only transient, right? >> Okay. The key here, and it'll make sense later, but the key for them was to find
19:53a cycl, a particular sort of um factor here that is like starting the cell cycle that is essential for one part of the cell, but if it sticks around for too long, then it's going to completely destroy the cell cycle. >> Interesting. >> Right. With the with the starter that you have on the grill, it's going to be annoying. The sound is going to be annoying, but the grill is still going to work. Yes, >> we need to find a type of starter molecule that if it sticks around is going to be deadly >> for later. And what they found is a cycl CLB5. What this thing does is promote DNA replication. So essential, right? This is the thing that starts DNA replication for the cell. But it
20:34naturally gets degraded and if it's still present, it's going to lead to cell death. >> Okay? >> Because of later on, it's just going to mess with whatever whatever is going on. It's not important like how it does it, but we just know if it sticks around, it's bad. CLB5. Okay.
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