 All right, we're going to practice because that was like 20 minutes of a very long explanation for how we can determine the sequence of DNA nucleotides. But we still like really it's not like it's kind of vague and hard to visualize. So I have a have a present for you. I have another actual gel over here on the right side of this visual. And so that you can see that, OK, I can see how there are blobs, dark lines of DNA in this gel. And you can see that not all the fragments moved the same. They move different speeds and they've figured this works. So I created a I don't know what is this thing? It's just a diagrammatic view of I just made it up. So it's a gel. I labeled the positive end and the negative end. So this is the direction of the current. If you are given nothing else, if you can figure out which end is positive and which end is negative, you can figure out the direction that the particles are going to move and then predict where are we going to have small particles and where are we going to have big particles? Remember the ones, the big ones are going to go slower through the gel. The small ones are going to go faster. So the big the the lines that we're going to see closer to these wells, those lines are going to be bigger pieces of DNA. Even one base pair, one base difference. If I have five bases or six bases, the six base piece isn't going to go as far as the five base piece. And we know that all the fragments in column one end with the nucleotide A. And all the fragments in column two end with the nucleotide T and then G and then C. So watch what we can do. I personally start at the top even though like you can start anywhere that you want. I'm starting at the top. I'm starting at the top and I'm just going to use a highlighter and I'm just going to highlight. I'm not going to like using a highlighter. So I changed my mind. I'm going to use yellow and my very, the smallest fragment ends in the letter A. Do you agree with that? Maybe I'll just change colors as we go. So then as I change them, you can keep track because again, like, can you even see this? The next one, I just want you to know I made this in Excel. So there is a next one and it is a box that is in Excel because this whole thing is like a grid. My very next one is in the T column. So my next base is a T. My very next one, let's see, is in the C column. Do you see how I'm doing this? So my next base is a C. My letters are not quite lining up because I'm writing them bigger than the well or the line in the gel is. But the next base is another C. The next one lines up with a G. Do you see what I'm doing here? The next one lines up with a T. And the next one is an A. Do you see how I'm doing this? And then we have another A. I'm trying to color code it so that you can see that I'm actually reading them. I'm not reading them down. Like, I have to pay attention. I have to be really careful when I do this because this is base number one. Here's base number two. Here's number three. Here's number four, right? And so I put them in that order. In that way, you can do the whole thing and you get the entire sequence. Now if you want to be super awesome, I was going to say badass and then I was like, dude, can I say badass? And then I was like, oh, look, I just said it anyway and I'm not redoing this. Okay, whatever. If you want to be super amazing, you can go through and you can go, okay, what's the other side? Well, you can get the whole thing right. Do you see what I'm doing? I'm making my double strand of DNA. Then you definitely can be super awesome. You can be like, dude, I'm going to get even crazier. I'm going to figure out what the mRNA is. You can do that from the A. We would go U, A, G, G, C, A, U, U. You want to get even cooler? You know I can't show you this because I didn't prep it, but you could take the mRNA and figure out what amino acid it codes for. You could do the whole thing. You can just from that sequence. Guess what? Yes, you will have lots of practice with this because yes, it is something that we are going to do. Okay, now we've got the sequencing down. We're going to look at two types of tests that were done for COVID. When you were exposed or you had to go back to work or you had symptoms, we did two kinds of tests. We did PCR tests and we did antigen tests. We're going to talk about how both of those work.