hi everybody welcome back to miss Angler's biology class I am Miss angler in today's video we are going to be looking at DNA profiling I'm going to walk you through how they create a DNA profile and most importantly I'm going to show you how to read one in an exam or a test and how to explain the reasons why you potentially chose the person or the victim or the parent from the choice making sure that you get four marks every single time now if you are new here don't forget to give this video a thumbs up and make sure you're subscribed because I post new videos every Tuesday and Thursday for grade 8 to 12 Life Sciences also if you are in matric and you're thinking about getting that distinction at the end of the year and you want a little bit of extra tuition from me then maybe you should join my membership and you can find that on my home page you just simply click the join button and you select the option that you would like to have so let's jump into this video now the most important thing I want to stress here to you is the difference between DNA profiling and DNA fingerprinting in the exam and I'm talking about specifically the final exam we are only ever going to refer to this process as DNA profiling and basically a DNA profile is looking at the entire uh set of DNA that a person has and we select out sections that are unique to you and we want to determine whether the blood left at a crime scene is it yours is it another suspects we want to use a DNA profile to determine the paternity of a child so who is the father of that child we could also use DNA profiling to determine if you have a genetic disorder or if we need to identify the human remains that are left behind and we have a sample to compare it to we can use DNA profiling to do that now depending on the level that you are doing this particular topic on some of these things you don't need to know as much detail but I will say this if you are studying the South African curriculum you don't need to know a lot of detail about how we make the DNA profile you need to know more about how we read it however I'm still going to give you a basic understanding of how we make a DNA profile because there are three important things that you need to know about it in your final exam now it's at this point that if you are not very familiar with the structure of DNA and what makes up a piece of DNA then I suggest you keep the click the video above now which will take you back to an introduction to DNA so that you're more familiar with the terminology I'm about to use so I had this picture in front of us here now which is a piece of DNA it's a molecule of DNA and if you're familiar with the structure of DNA you will know that right now we're looking at the sugar phosphate backbone over here and then we've got these purple and these like turquoise um sort of runs or steps moving through it and those are the bases and ultimately when we are creating a DNA profile we are trying to find sections so let's say from here to there we are trying to find sections of DNA that are unique to you and generally the things that are unique to you are referred to as s t RS or short tandem repeats and what they are is they are repeats of certain letters that are unique to you now when I say repeating letters I'm referring to the code that DNA is written in so is it AAA repeated or maybe it's c a c a repeated so those are short tandem repeats and they need to be fairly short so they're not like whole pieces of DNA but those are actually the things that make you unique and that's how we tell the difference between people and we can identify criminals or we can identify fathers and mothers so now let's look into how do we actually make this DNA profile and I want to just remind you again please do not call it a DNA fingerprint you will not get the mark for this in the final paper it is a DNA profile now the first thing we need to talk about is the actual process now you do need to know this name it is gel electrophoresis this is the process that we use in order to create the profile that we're going to look at now this is where um sometimes your teacher wants you to know a lot more detail than others so I'm going to run through it and then I also want you to know that at the end of the year you don't need to know this much detail you do need to know the name of the process being electrophoresis but other than that I'm going to highlight two other things you need to know and that's really it but let me just show you how we actually make it so what we do step one over here is we take a blood sample we extract DNA from your blood sample specifically your white blood cells because red blood cells don't have DNA in them and then what we do is we cut into your DNA using a restriction enzyme now that is the second thing that we need to know for our final exam and that is the thing that cuts up your DNA into pieces and what are we cutting those pieces into we are looking for those strs I mentioned earlier we then take those DNA fragments we put them into the electrophoresis machine and it's got like a gel plate within it and what we do is we run an electrical charge through it and when we put that electrical charge through it what happens is if this is the plate we put the DNA at the top over here in these little windows and then depending on how big or small the piece of DNA is if it's very big it will remain quite high up on the plate but if it's very small it'll move lower down and what you end up getting is what sort of looks like a barcode and this barcode references this person's particular DNA but now we need to be able to see this DNA right because DNA is microscopic so the next thing we do is we wash off the excess DNA and we use a radioactive probe which basically means what we do is we make it visible by making these little bands actually glow and that makes them more visible now that they are more visible we go over to this point over here step 10 and 11 where we can actually see these bands and they are visible and someone will read those bands and be able to tell you whether or not this person is the criminal are they the father Etc now the third and final thing that I said we do need to know out of this process is what do we call these like stripy bits right so according to the guideline we can call them a band or we can call them a marker I prefer genetic marker because it is a little bit more accurate of what it is but you can use either one of these words to describe um the let's say the image that is produced and you'll see I'm going to use those words now to describe how to read different DNA profiles now what we're going to do is we're going to look at how do we actually read a DNA profile and there are two of the most common forms that we will see in exams and tests and this is what I always tell my own Matrix to do and it always works out the best for them and they always manage to figure out um who potentially the father was or who the suspect is so we're going to start off with a reading a DNA profile for a paternity test and let's remember the opportunity tests are testing for who is the father of the child because the mother has already been established now what we need to do is get a ruler and a highlighter when we're in the exam or a test and you're going to cover up everybody's markers right with your ruler and you're going to slowly drag your ruler down and as you drag the ruler down the Mark or the first Mark that aligns with the child you need to see where that aligns with all the other parents so if I'm looking at this child and I'm going down the list this one over here is our first Mark so we highlight that and we look across to both the mother and to the fathers and we highlight the fathers that also have those bands in place we do the next one and we see that aligns with the mother and we carrying going down and we get to this next ball of the child and it aligns with this mother here and then this Dad but not the dad too because you see it's slightly off it's not perfectly in line it's got to be perfectly in line and that's why our rulers really helpful we then highlight this next one and we've got this Dad here and then three the next one from the child is this one here and that one there and then last but not least this bottom line is in line with the mother and not Dad one because they are not perfectly aligned now looking at the three profiles who is the father of the child well what we're looking for is the father with the most genetic markers in common which is going to be Dad number three because he has three markers in common now this is the important bit when we are an exam or a test often they'll ask you to identify the father and then give a reason why you selected that father and this is what we're always going to provide when we are explaining your reason for parents so when explaining you need to state that 50 of those markers match the mother and 50 of the markers match the father and when I talk about a marker I mean those bands or those dark lines that we see there and that's actually kind of how it makes sense and that that's how we make children right uh children are 50 of their mom and fifty percent of their dad so if this child has six bands which they do then three will come from Mom and three will come from dad sometimes it's slightly uneven and you might get Mom will have four and Dad will have three but that Dad is the only one with those three then that's perfectly fine potentially that just is not an error but maybe that is a band that wasn't passed on to this child or wasn't tested in that profile but that's the reasoning you're always going to give in an exam now what we're going to do is look into crime scene investigations at this time we are looking for a suspect perhaps there was some blood left at a crime scene and now what we need to do is we need to establish does that blood belong to the victim or did somebody else leave it behind and then we can identify that specific suspect so you do exactly the same thing take your ruler you're going to cover up all of the bars and you're going to slowly drag it down and you're always going to compare the crime scene bar to the individuals so we're going to go our way down and we're going to highlight all of the bars that match up with the crime scene and it's okay if you notice as I do the next one that there might be bars that they're all share and that is going to happen because that is the nature of genetics we are all humans so there is definitely going to be um genetics that we all share so it's not uncommon to find that and we go down and we make sure that we highlight all the bars that are shared with the DNA I think that's it right so now even though suspect 1 and suspect 3 do have some bars that are present on the crime scene DNA we need to make sure that all of the genetic markers or all of the bars that we see at the crime scene DNA must match all of the suspects and there is only one individual that has all of the bars present and that's going to be suspect too okay you'll see they're all there it's actually a mirror image exactly the same so what do we say in exams well when we are identifying a criminal you need to use the following explanation you need to say 100 of the markers match the DNA sample and and when saying that we don't want to confuse it with the um paternity test where we do 50 50 it must be a hundred percent now as always I'd like to finish off my lessons with the terminology recap and you can use these words for flash cards which makes studying so much easier speaking of flashcards all of my flash cards are now available to purchase there are over 500 flashcards available you can get them on my website there are on every single topic you need to know for Life Sciences for the final exam they are complementary to the study guide so if you have the study guide it's perfect and even if you don't have the study guide the flashcards are going to make your life so much easier to study from but getting into the recap the beginning of the video we spoke about strs which are short tandem repeats those are the letters that are repeated uniquely in each person and they are the things we use to create DNA profiles and those strs are made out of repetitive bases so like the letter A A A or a c a repeated quite a few times we then used a gel electrophoresis machine to create the DNA profile and we use something called restriction enzymes to cut up the DNA into the pieces before we form that DNA profile with the gel electrophoresis machine we then also looked into the uses of DNA profiles and we looked at paternity so looking for a father crime scene so we're looking for the suspect and lastly as I mentioned we could also use them for genetic disorders which means we identify people who potentially have certain disorders before they are born even or if they are already born we can tell them you have a 60 chance of maybe developing Alzheimer's because you have the genetic markers for it now if you like this video don't forget to give it a thumbs up and make sure you are subscribed and I will see you all again soon bye [Music]