okay on to the next genetic technology that we have to talk about for this chapter we are going to be covering something known as gel electroforesis now this particular technology is just a method of separating either DNA molecules or protein molecules depending on their charge and mass we are not separating both of them at the same time by the way it's either there are two types of electroforesis protein electroforesis where we separate proteins or DNA electroforesis where it's separating DNA molecules only and the separation is based on their charge and mass of the molecules and the pictures that I'm including down here um uh through DNA electroforesis when you separate the DNA molecules according to their charge and mass they will produce those patterns and those patterns are referred to as DNA fingerprints so the focus on this chapter however is going to be on DNA electroforesis only the first thing that we have to understand here for DNA electroforesis as mentioned is separating DNA fragments based on their charge and Mass to produce bending patterns or DNA fingerprints and just to reiterate my point these are examples of the bending patterns now why would we actually do DNA electoral foris number one we can use it for forensics when we talk about forensics we are talking more on the crime scene I'm sure you guys have watched like some crime shows or some crime trauma and they will tell the person or the suspect we found your DNA in the crime scene how did they exactly find the DNA in the crime scene that's what they're talking about the DNA fingerprints we also use DNA elect phoresis on paternity testings when we want to confirm whether the child belongs to actually came from the father's DNA or did not come from the father's DNA uh that's more on the family side of things and also we can use it for genetic screening because we can use DNA electroforesis to detect specific alil in the person I will show you how DNA electroforesis is used in genetic screening at the last part of this video later so just hang on now for DNA electroforesis to happen there are a few requirements number one we need the DNA fragments obviously to get separated uh and for my example here please do not memorize my example but I'm showing you four DNA fragments now some students will say where did these fragments come from don't worry about that part let's just focus on the fact that we have some DNA fragments right now so these DNA fragments ments I want you to notice that fragment a is the longest fragment B is slightly shorter C is much shorter D is the shortest DNA fragment or the smallest DNA fragment okay the point is I just want you to understand that these fragments have different length and mass the longer it is the higher the mass the shorter it is the smaller the mass the next thing that we also need is we also need something known as polyacryamide gel you don't have to memorize that name you can just say that we need a gel now the polyacryamide gel is a very interesting gel that is able to separate DNA molecules according to their Mass I will explain that later and the last thing that DNA electroforesis will always need is the electrical field you need to apply an electrical field of cathode a negative point and anod positive end um it's good to memorize that kode is negative and anode is positive but in the exam if you just say that DNA electr foris needs a negative end and a positive end that's good enough I always get those two confused I always think that codes are positive and anodes are negative I think the reason is because of chemistry because cations are positive ions and ions are negative ions so I get you know sometimes even my brain you know has that the wires cross in my brain sometimes and in short circuits so just mentioning a negative n and positive n is good enough what what I'm going to do here is I'm going to draw out the container a three-dimensional container and it's filled with the polyacryamide gel but what I'm also going to do here is I'm going to show you the top view so the top view is we're just looking at how the gel is supposed to look like we will then apply the negative field and the positive field okay that that's done by using specific uh electrical components we don't have to go into the detail of that but you can see that the kathode is at the you know this end and the anode is on the other end and at the negative end or the cathode end we also dig up a well a well just means that we kind of remove a little bit of the gel and at that area we apply the DNA fragments now if you notice it's there are many DNA fragments over there there's a lot of DNA fragments a there's a lot of DNA fragments b and a lot of DNA fragments c and a lot of DNA fragments D so how did we manage to get copies of a b c and d obviously we managed to get copies of a b c and d using something known as polymerase Chain Reaction now there is a reason why you need to have multiple copies of a multiple copies of B multiple copies of c and also multiple copies of D the reason is because if you have only one molecule of a b c and d the results will not be so clear so to make the results more clearer to produce those thick thick fingerprint bands that I'm talking about you need to have multiple copies of each DNA fragments how do we produce multiple copies of H DNA fragments just run it through polymerase Chain Reaction now what I want you to understand here is the DNA molecules are all kind of collected in the well they're not separated yet by the way and we will put the DNA at the negative end now why do we put the DNA on the cathode or the negative end of the apparatus this gel electroforesis setup the reason is because DNA is inherently negatively charged if you remember in the DNA molecule which are made up of DNA nucleotides they have the phosphate groups which I've highlighted over there in yellow the phosphate groups are ions which are negatively charged so DNA is inherently negative okay so when you put them at the negative end and you basically put the positive end on the other side what will actually happen is it forces the DNA to move to the positive end because DNA which is negatively charged will be attracted to the positive end of the gel so negative molecules are atted to the positive side that's the logic of it now the thing over here is by putting it in something known as the polyacryamide gel it will provide resistance resistance just means that okay imagine if you were in a you were just walking like normally and you have no problems walking from one point to another point but imagine walking in a pool of water you're in a swimming pool and you're trying to walk from point A to point B you will have more resistance the same principle applies here the gel that polyacryamide gel will provide resistance and it makes it so that the smaller fragments will travel much further than the larger fragments so as you can see here yes all the fragments are negatively charged and they'll all move to the positive side the anote end however molecule D has the least resistance because it can wiggle through the space within the gel and move the furus however at that same period of time molecule a which is the largest will move the least because it has the largest mass and it's the longest it will have the most difficulty moving through the gel some students will argue that molecule a should have more negative charge so it should move further and molecule D has less negative charge so it should move lesser because it has less phosphate groups the problem here is the mass supersedes the charge so the mass of the molecule influences whether it moves further or Not by the way so at this point over here what exactly happens after a certain period of time you will notice that it will produce four bands now what exactly are these four bands all about and this is the DNA fingerprint right here so it will produce these four bands and those four bands will correspond to a b c and d a traveled the least because it is the largest DNA fragment D traveled the most because it had the shortest DNA fragments remember if you only had one copy of a one copy of B one copy of c and d you will not be able to see those fragments clearly so you need to have multiple copies of them that's how they produce these DNA fragments now as an example let's see how we can use gel electroforesis to screen or to detect a genetic disease now as an example do not need to memorize this but a gene for the genetic disease has the large B alel which is normal and the small B Al which uh causes the disease to happen so and I'm just going to draw out the DNA fragments the chromosome the large B has that length the small B has that length but interestingly if we use a restriction enzyme to cut the large B alil it cannot be cut the reason is probably because there is no restriction sites or no areas where the enzyme can cut the large B alil but it so happens coincidentally the small B because the B sequence is slightly different it can be cut using the Restriction endon nucleus and it will be cut into two fragments as you can see there it's cut into one large is fragment and one small fragment right that now three people go to the hospital and there are the three people's name are as follows matusa lamia and bit don't the names just came randomly okay it's uh Laman and Barett if you play Persona 5 uh you would know that these are just some of the personas anyway so these people went to the hospital to check whether they have the disease so what the scientists did were they actually checked the DNA and they put the DNA into the gel and separated it according to DNA fragments interestingly for methusa they only had one band forming for Lumia they had two bends forming at the bottom and for barit they had three DNA fragments forming so what does that tell us the one closest to the well is the largest fragment medium and then smallest fragment so what are the genotypes of methusa lamia and barit in this case over here we know for the fact that matusa has to be large B large B how do we know they only have the large B large B Al because they only have that alil like that that alil could not be cut so that Al will get separated and it's the largest it will get separated over there so they only have large B large B alil simple as that lamia however will probably be small B small B Because fragment because they have the small B Al the alil could be cut into two fragments where fragment number two will get separated over there fragment number three which is the smallest will get separated the furthest that's what happens what about Barett I'm just going to give you about 10 seconds to try to figure Barett out if you guessed that Barrett is large B small B you are right because they had the large B Ali which is separated over there and they have the small B Al which are separated there and also there there you go so that is how we can use gel electroforesis to detect the presence of specific diseases or even predict the genotype of a person so I hope you understand this one