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Main content
Current time:0:00Total duration:3:45
AP.BIO:
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Video transcript

but there are other higher levels of regulation that occur here and I started to talk about them when I mentioned our RB protein so control control of the cell cycle occurs on a higher level with a couple of key proteins in addition to our B one of the main proteins we talked about that regulate on a very high level is p53 it's even got a nickname it's the guardian of the genome the guardian of the genome it's so important actually that science magazine called it the molecule of the year in 1993 theobromine the main molecule that's in chocolate hasn't even gotten this honor yet so it shows you how important p53 is it's more important than chocolate p53 will bind DNA directly to produce proteins that block the progression of the cell cycle one of those proteins include p21 p21 will function to inhibit cdk and so the cdk will not be able to activate DNA replication or activate mitosis RB is another protein that's associated with the function of p53 and these proteins are considered tumor suppressor genes so RB is a protein that's produced from a tumor suppressor gene just like p53 so I'll write that down over here these proteins are considered tumor suppressor genes tumor suppressor genes they're made from tumor suppressor genes I should rather say these proteins are made from tumor suppressor genes which are important to have because if they're defected or if they have a mutation in them that makes them have loss of function so that's an important term defected or if they have a loss of function loss of function what ends up happening is that you tend to get you tend to get cancer cancer which I think you and I can both agree is not a good thing to have so it's very important to have tumor suppressor genes and to illustrate how important that is if you look at p53 greater than 50% of tumors have a defect in p53 RB got its name because a defect in RB would lead to a tumor of the eye known as ret - no that's where you got the r retinal blastoma retinal blastoma which is why these two proteins are considered tumor suppressor genes p21 is very unusual in that it doesn't actually lead to cancer when it's defected instead scientists have found that mice mice that are without p21 have the ability to regenerate their limbs how weird is that p21 lack causes the ability to regenerate their limbs their arms and legs so we're all still trying to figure out exactly how some of these key proteins work but it's important to understand that tumor suppressor genes are essential for making sure that we regulate the cell cycle so we don't just go to the divide divide divide phase we want to make sure that we divide when it's appropriate when a cell is ready to or if it's even a cell that's supposed to divide in the first place because as we'll see in our next couple of videos mitosis or cell division requires a lot of energy and protein machinery to happen so we need to make sure it's the right time to divide
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