If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:12:03

Video transcript

so in most people right when we're talking about their Parkinson's disease we say that their Parkinson's disease is idiopathic and that just means that we don't know what caused it and that's actually the case for the vast majority of people with Parkinson's disease about eighty-five percent of people so it's a lot right but in a handful of people with Parkinson's disease about 15% we actually do know what caused the disease and for these people something's actually gone wrong with at least one of their genes so a quick recap on genes remember that genes are essentially specific segments of our DNA right so you'd find them in almost every cell in your body so there are specific segments of DNA that provide instructions to the cell and each gene is like a special recipe so each gene has instructions for how to make different proteins and once these proteins are made they go off and they do tons of different tasks tons of different important tasks all around our bodies like well basically everything basically everything is done by proteins from creating our cellular structure to our organs to our enzymes those are proteins to essentially every structure or process in our bodies that you can even think of absolutely everything somehow involves proteins so when something goes wrong with our genes let's say it's supposed to look like this right but maybe due to a mutation a change in that gene it ends up actually looking kind of different so maybe something like this here now all of a sudden the instructions the recipe that that gene has for making their proteins they're not correct anymore right they're not the same and so the proteins that should be made the proteins that we want these genes to make now they can't be made properly anymore at least in cells that have these genes that are affected that are changed that are mutated and when proteins are made properly well they won't be able to carry out their normal roles anymore right so we actually have a collection of genes a family of genes that when they're changed when they're mutated in some 'we can either directly cause or increase our chance of developing Parkinson's disease and this depends on on which gene gets mutated now remember how we get our DNA how we get our chromosomes so we have 23 single chromosomes that we get from our dad and we get another 23 single chromosomes from our mom and they form pairs so we end up with 23 pairs of chromosomes right so that means that we have two copies of each gene right one copy came from your mom and one copy came from your dad now let's actually classify genetic causes of Parkinson's disease into two groups so two types of inheritance if you will so we'll say autosomal dominant over here and and we'll say autosomal recessive over here on this side and this will all start to make sense in a minute here and the inheritance patterns can get really detailed and messy so I'm not going to really go into all of that at the moment but basically I want to get across here that the autosomal dominant types of Parkinson's disease or really any other disease that's inherited in an autosomal dominant way you only really need one bad copy of the gene so either one bad copy from your mom or one bad copy from your dad and that would be enough to cause the disease so in this case in our case that's Parkinson's disease and autosomal recessive well that means that both mom and dad need to pass on to you a mutated copy of the gene and there's one other thing I should mention so so when we say that a gene mutation causes a disease so in this case we say a gene mutation causes Parkinson's disease we can either mean that it definitely causes the disease 100% so if you get the mutated copy or if it needs two copies of the gene you will definitely develop the disease or we can mean that getting the mutated copy or copies will increase your chance of developing the disease so those two things are a little different right and for some genes certain mutations within that gene will definitely cause the disease and other mutations in that gene may just increase the chance of a disease developing and that's because different mutations in Jeane affect the genes protein in different ways right so some mutations may be more detrimental than others so that can increase the chance of disease developing so as we're chatting about these these mutated genes that we're going to get to that are relevant to Parkinson's disease we're just going to say that they can cause the disease but in the back of our minds we just have to remember that depending on which specific mutation in the gene is happening because there can be quite a few different ones in one gene and this is still being researched right the mutation can either 100% cause the disease or just increase the chances of developing the disease okay so there are five main genes that we know about so there are a few more but there's five main ones that when they're mutated in some way can cause Parkinson's disease so we won't go into all of these genes but let's go over a few of the genes that are a bit more commonly mutated so let's head over here to our first chromosome chromosome number one so here's our first chromosome so it's just it's just hanging out here and and right about here we have a gene called Park seven and park seven it has instructions for making a protein called DJ one so here's DJ one here and and DJ one kind of makes me think of a mom when I think about what DJ one does I think if I think of a mom it does things like protecting and guiding right protecting and guiding our molecules around our body you know like how your mom protects and guides you right so it helps protect ourselves it helps protect them during situations that stress ourselves out and and it helps guide our proteins so it helps guide them to do things like make sure they're folding in the correct three-dimensional shape because remember that our proteins are proteins need to get into a certain shape in order to be able to function properly right and dj1 also helps to make sure that damaged proteins proteins that we we don't want anymore are sent off to be broken down because otherwise they kind of pile up in our cells and they get in the way right now this last ones not very mom-like I'm sure none of our moms would send us off to be degraded but anyway so those are some of the main tasks of dj1 so some mutations in the gene park7 can cause Parkinson's disease park7 is one of those genes where you need to get a mutated copy from both your mom and your dad in order to develop Parkinson's disease so this would be considered an autosomal recessive cause of Parkinson's disease and it's actually responsible for early onset Parkinson's disease so so Parkinson's that's diagnosed before the age of 50 years old so when park7 is mutated when the genes DNA is changed in some way that changes the instructions on how to make the dj1 protein right because the gene carries our recipe for that protein so when this has changed dj1 isn't made properly and therefore it can't function properly it can't do all of these important mom-like tasks that we talked about so that's park7 and dj1 so what's our next gene let's let's jump over here to chromosome 6 and let's check out our next gene so about about here on chromosome 6 about here this is this is where our Park 2 gene is and for a mutation in this gene to cause Parkinson's disease it would need to be inherited in an autosomal recessive way as well a mutated copy from both your mom and your dad oh and something that's really interesting is that the park 2 gene it's one of the largest genes that we humans have in our whole body so it's one of the biggest genes that we have so park2 it encodes for a protein called Parkin so let's draw let's draw a little Park in protein here and Parkin has this really really important role what it does is it tags other proteins that are damaged or or that we have too many of there they're in excess and it tags them with this molecule called ubiquitin so ubiquitin is like a it's like a little flag it's a flag that alerts ourselves to shuttle these proteins that we don't want that we don't want anymore and it alerts them to shuttle them to these structures in our cells called proteasome and this is where those proteins that we don't want get broken down and disposed of so proteasomes are kind of like the the waste disposal facility in our cells so parking is really really important from making sure that we don't have all these excess or damaged proteins kind of piling up in ourselves and getting in the way so we actually know of a couple 100 different Park two mutations that can cause parkinson's disease so some of these mutations are associated with the juvenile form of Parkinson's disease which is essentially an extremely early onset type of Parkinson's disease relatively speaking to when it normally comes on so when people are diagnosed before the age of 20 and some other park2 mutations they're associated with late onset Parkinson's disease which is when people are diagnosed after the age of 50 years old but in either case whether it's early or late Parkinson's disease these mutations have changed the gene a bit right they've changed our instructions for making Parkin and so we end up with a non-functional Parkin protein a Parkin protein that just can't do what it needs to do it can't function properly it can't tag these damaged proteins so that we get rid of them so our last gene that we're going to look at is is over here on chromosome 12 so here's chromosome 12 here I'll just draw it out and the gene that we're interested in is the LR rk2 gene so I'm going to call it lark - it's just a little easier to say and and it sits about here so so lark - gives us the recipe to make the protein dard erin and dart erin helps us do things like turn our cells on and off so that we can control their activity and and send signals around the brain so that different cells can talk to each other and what's really interesting is lark - mutations are actually the most common gene mutation that is associated with Parkinson's disease so this is the gene that we normally see issues with in people that have a genetic form of the disease and with this particular gene people only need to get one mutated copy from either of their parents rather than both so this is an autosomal dominant genetic cause of Parkinson's disease and just like before when when our lark - gene gets mutated we end up with a malformed a damaged dard erin protein being formed right so it's being produced by transcription and translation but because we've damaged the lark - gene in some way the instructions are all wrong so the protein ends up being formed a little differently so it can't function properly in order to carry out its really important roles so we've gone through some of these gene mutations that can as Parkinson's disease but by now you must be wondering yeah I get that I get that Park seven and park two and lark two can get mutated and produce malformed proteins and then they can't do their jobs correctly etc etc but what does that have to do with Parkinson's disease how does that cause Parkinson's disease and that's an excellent question and and the answer as it stands right now is that we actually don't know we don't know how these genes getting mutated and these proteins being malformed we don't know how that actually leads to the disease we just know that we consistently see Parkinson's disease development in people with these gene mutations but we don't yet know kind of step by step how people with these mutations actually develop Parkinson's disease so for now we'll just have to stay tuned into the ongoing research efforts to find out more about this one