Use the genetic code above & the coding DNA sequence below...

Question

Use the genetic code above & the coding DNA sequence below to determine the protein sequence.

DNA coding sequence for protein sequencing in biochemistry chapter 5.

Accepted Answer

Alright. So this practice problem wants us to use the genetic code above and the coding DNA sequence below to determine the protein sequence. And so notice up above, we have our genetic code, and down below, we have our coding DNA sequence. And so, what you'll also notice is that this genetic code here is specific to mRNA codons, and we know that because it has uracils in it instead of thymine. So uracils are found in RNA and thymines are found in DNA. And because we're giving a coding DNA sequence, we first need to convert it into RNA to use this genetic code. Now recall from our previous lessons that a coding DNA sequence, because it's coding, it's going to have the exact same sequence as the mRNA sequence, except in the mRNA, all of the thymines are going to be replaced with uracils. And so if we go ahead and highlight all of the thymines in our DNA sequence, we can see there's 1 here and, one there, 2 here, and one here. So we have a total of 5 thymines, and all of these thymines are going to be replaced as uricels in the mRNA sequence. So if we're providing the mRNA sequence, essentially it's going to be exactly the same. So we're going to have an A here, and the t's are going to be converted into u's. So we have a u g, and then we have g c c, so g c c, then we have u g c g u u, cu c u c a a g. And so this is in order from 5 prime to 3 prime. And this is our mRNA sequence. So now that we have our mRNA sequence, we can use the genetic code above to read out the codons, which are sets of 3 nucleotides in the mRNA. So our first codon is gonna be AUG, and then our second codon will be GCC, then it's UGCGUCUC, and last but not least is AAG. And so, what we can do is read these codons, so that we can determine what amino acids they correspond to. And so again, our first codon is AUG. So the first codon in our genetic code, the first base of our codon is going to be on the left hand side. So because it's A, that limits us to this whole row. The second base is u, so the second base is at the top. Because it's u, it limits us to this whole row I'm sorry, column. And then the last base is g, so it limits us to this exact position within the box that we're limited to. And so AUG corresponds with a methionine amino acid residue. And so down below, what we can do is put methionine, or one letter code m, for this codon. Now moving on to g c c, g is this row here. C is this column, so now we're in this box. And then c, limits us to this exact position, which corresponds to an alanine. So down below, we can put alanine for GCC. Then we have UGC, so u, g, and c limits us right here to this position, which is a cysteine. So down below, we can put c. Then we have GUU, which is going to be g, u, and, essentially, we're in this box, so gu is right here, so veiling. Then, you guys can get the hang of how this is going. We got c u c, so c, u, and c limits us to this position right here, so that's a leucine. And so down below, we can put l. And then a a g, our last residue, is gonna be a a, and that limits us here. So we have a a g, so shown here. So that is a lysine, and so lysine's will enter code as k. And so essentially, when it's asking us to determine the protein sequence, the protein sequence is going to be this protein sequence here. And because we have our arrow pointing this way, we can put our protein sequence over here on this side of the arrow. So essentially it's going to be methionine, alanine, cysteine, valine, leucine, and lysine. And so this here is the answer to our practice problem, and that concludes this practice. So I'll see you guys in our next video.

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Use the genetic code above & the coding DNA sequence below to determine the protein sequence.

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