Genetic Code

in this video, we're going to begin our lesson on the genetic code, and so the genetic code is just a table. It's a specific table that reveals how DNA and RNA encode the sequence of amino acids in a protein. And so the genetic code is really the link between nucleic acids, like DNA aren't a and the amino acids of a protein. Now the genetic code is relatively universal or relatively consistent across all organisms. But it can have some differences between different species occasionally, and the genetic code analyzes one code on at a time and recall that a code on is a three nucleotide sequence that's found in the messenger RNA. The M Arna and each code on each three nucleotide sequence is going to specify or reveal one particular amino acid. And so we use the genetic code to analyze one code on at a time, revealing one amino acid at a time. And so we'll be able to talk about exactly how to use the genetic code in our next lesson video. So I'll see you all there

in this video, we're going to talk about how to use the genetic code. And so notice down below, Over here, on the right hand side of our image, what we have is the genetic code. And so how exactly do you use this genetic code? Well, it turns out that using the genetic code is really just a three step process and notice that we have each of those three steps number down below here. And so the very first step of using the genetic code is actually to use the coding DNA sequence to reveal the mRNA sequence. And so, really, this is the process of transcription using DNA to make Marna. And so, of course, we know from our previous lesson videos that the Marna sequence is going to be exactly the same as the coding DNA sequence, except for the fact that it's going to be replacing all of the tees or thigh means with use or your cells and the Marna. And so if we take a look at our image down below over here on the left hand side, notice that we're showing you a DNA molecule which we know has two strands. One of the strands is going to be the DNA coding strand, which is gonna be this top strand here. And the other strand is going to be the DNA template strand, which will be the bottom strand here. And so, of course, we know from our previous lesson videos that the Marna sequence is going to be exactly the same as the DNA coding strand, which is the top strand. So the top strand is the one that we want to focus predominantly on. And so again, it's going to be exactly the same as this top strand. Except it's going to be replacing all of the tees or thigh means with use. And so, as we start to reveal the Marne a sequence we can see here we start off with a T G. And so we will put a and it's tempting to put a T here as the Marna. But we need to remember the NMR on a there are no teas and that the teas will be replaced with use or your cells. And then, of course, we have the G. So then we can continue to do that, just you literally rewriting the coding sequence except replacing the teas with use. And so when you do that, you get see a you, you get a C c. Here, you get you g you at this, these positions and then you get you a a here. And so now we've revealed the RNA sequence, and step one is complete now and step to. What we need to do is identify the three nucleotide coding frames within the Marna transcript. The Marna molecule is sometimes referred to as the Marna transcript. And so identifying the three nucleotide coding frames includes identifying the start code on which is typically where the, uh the first coat on of the Amarna and also identifying the stop code on a swell, which is typically going to be the last coat on. And so if we take a look at our image down below, we can kind of see Step two is already been done for us because these dotted these vertical dotted lines that you see at these positions are kind of separating our Marna into these three nucleotide code ons. And so you can see here that we have the first coat on would be a you G. Then we have the second co down would be C au and then we have a C c and you g you and then last but not least you A. So those are the co dons and noticed that they've already been identified because we have separated them with these dotted lines. So step two is complete. And so, in Step three, all we need to do is identify the amino acid that corresponds with each of the code ons until a stop code on is reached. And so the stop code on is going to stop the process because it does not actually code for an amino acid. And that's why the process stops at thes stop code ons. And so, of course, in order to identify the amino acids that each code on corresponds to, we need to use the genetic code over here. And so the genetic code is going to show the very first letter of the code on on the left hand side of the table. So you can see the first letter of the code on here is going to be here, and the first letter of the code on will limit us to a specific row. Then, of course, the second letter of the coat on is going to be across the top and so across the top here we will find the second letter of the coat on, and the second letter of the coat on is going toe. Limit us to a specific column. And so, between the first and second letters, it will limit us to a specific box where they overlap. And so a to this point, we would be looking at just one specific box here, and then the third letter of the code on is going to be over on the right hand side. So you can see the third letter is over here, and that would limit us to a specific position within the box so that it would reveal a specific code on. And so the genetic code shows all of the possible code ons and linking these cordons to amino acids. And so here, in our example, what we're going to do is determine the poly peptide sequence or the protein sequence down below here from the following DNA sequence. And so we already have used the DNA to reveal the Marna sequence. So now we need to use the Marna code ons to reveal the amino acids in the poly peptide. And so it will do this one code on at the time, starting with the very first coat on here A you G. And so the very first letter of this code on is a So the first letter of the coat on is over on the left hand side and a is going to limit us to a specific wrote. Then the second letter of this code on is you and you is going to be the second letter. The code on is across the top, and you is gonna limit us to a specific column. And so where these two overlap would be right here in the middle. And so where this yellow region is, so we can kind of get rid of this to see it easier. So now we're focused on this particular box that's highlighted in yellow. Then we look at the third and final code letter of the code on which is G. And the third letter of the code on is going to limit us to a specific position within the box. And that takes us right here. Since we have the G, you could kind of trace it all the way over and see that it's right here. A you g and so a You g is. The code on is found right here. And it turns out that a U. G is typically the what they call the start code on. It's the very first code on of most proteins. And so it actually codes for an amino acid called Mutthiah ning, which is abbreviated with letters M e t. And so this first coat on here, the start coat on is going to be M E T. And notice that this poly peptide sequences amino acid sequence is going to be revealed from the end terminal of the protein to the C terminal of the protein and soma thinning is the very first one. So now we just need to repeat this process for all of the other code on. So we'll do this again and relatively slow here with c au. The very first letter of the coat on is C. So the first letter of the code on is going toe limit us to a specific row, then the second letter of the code on is A and the second letter Croton is across the top and a is right here. It limits us to a specific column. So now we're looking for where these two boxes overlap, which is gonna be right here in this yellow highlighted region so we can remove these and see, this is the box that we're focusing on. And then the third letter of the code on is you here. And so you the third letter of the code on is gonna limit us to a specific position. C au. And so what you can see here is that c au eyes the code on that codes for the amino acid history in which is abbreviated as h i s. And so here for C au we can put in a church, I s And so again we have revealed the first two amino acids for the first two coat on, and we just need to repeat the process again. So then we have a C, C and A is here. See, is here. So now we're in this box and then see the third letter of the code on its here. So you see a C c is right here. And that codes for a three inning amino acids. So that's th are abbreviation. Then we have you g you. The first letter of the code on is you. Second letter of the code on is Jeep. And, uh so that means that we're in this box. And the third letter the code on is you. So you g you is right here that codes for a Sistine amino acid C y s put that here and then last but not least, what we have is the last code on here, and the last coat on is going to be a stop code on that does not code for an amino acid. And so when you use you A in this, uh, what you'll see is you is here a is here. So we're in this box, and then the last letter of the code on is a so that's here. And so you a is right here at this position. And that is a stop coat on, and which will notice is that there are also three other stop coat. There are two other stop coat on three in total, and each of these code and does not code for an amino acid. Instead, they don't code for an amino acid, and they helped to trigger the the end of this process. And so you a here is just going to be a stop code on. There's no amino acid at this position. And so the poly peptide sequence is just going to be short, and it's gonna be right. Here is the poly peptide sequence. It is Matthiasson in history in three inning and Sistine. And so now we have revealed exactly how to use this genetic code. And so we'll be able to get some practice applying these concepts as we move forward through our course. So I'll see you all in our next video.