Suppose a mutation occurs in the DNA section in problem 17.89,...

Question

Suppose a mutation occurs in the DNA section in problem 17.89, and the first base in the parent chain, adenine, is replaced by guanine.

d. What effect, if any, might this mutation have on the structure and/or function of the resulting protein?

Accepted Answer

All right. Hello everyone. So this question says that a certain section of the DNA sequence shown here experiences mutation in which the cytosine in the sixth base is replaced by adenosine determine the plausible effect on the structure and function of the resulting protein of this mutation. So to understand the effect that this mutation is going to have on the resulting protein, we have to figure out the amino acid sequence both before and after the mutation. So first let me start by writing the original DNA sequence. So here I'll have two columns, I'll have the original DNA and then ill have the mutated DNA on the right side. So the original DNA sequence is CAA T AC G AC TG A. So going back now to the text of the question, the mutation is on position number six. So here let me actually start by copying this original sequence and pacing it here on the right side. The difference. However, is that now the mutated sequence is going to have adenosine instead of cytosine on the sixth position. So the mutated DNA sequence is CAA Taag AC TGX. Let me actually move this to the bottom just for visibility. So now for both DNA sequences, let's start by finding the MRN a sequence that results from it. So when it comes to this process of transcribing the MRN A sequence from the DNA sequence, we have to recall our base pairing rules, right? So that's adenosine pairing with Uracil or Adenine pairing with Uracil and cytosine pairing with guanine and vice versa. Now, because we're starting off with DNA A thymine on the DNA corresponds to Adenine on the Mrna. So using these rules, right, the original Mrna sequence is going to be guu A UG cug ac U. So now that we have the original Mr sequence, the good news is that we can use the same template for the mutated for the mutated MRN A sequence. But all we would need to do is change position number six to account for the mutation. So here if we go to position number six, that should actually be a U instead. So the mutated M RNA sequence is Gauucug ac. And from there, we can proceed with the amino acid sequence both before and after the mutation. Now, when it comes to translating the MRN A into a protein into an amino acid sequence, recall it. Here we take into account codons which are triplets of nucleotides that code for either one amino acid or a start or stop signal. So to reference, we would use our genetic code. So going back here to the original Mrna sequence. Our first code on is GU which would correspond to ving, that's VA L as the three letter abbreviation. Up next, we have a U which would be metin met. And then after that is cug which is lucine L eu. And from there we have AC U which codes for three need. That's T hr So really when it comes to the mutated MRN a sequence, all we have to do is change the amino acid for the coon that has the mutation, right. So the mutated base, sorry, the mutated nucleotide is on position six, which means that it's changing the second coon. So the first, third and fourth amino acids remain the same. So now looking at the mutated code on the mutated second code on which is a uu that codes for isoleucine ile. So now what does this change result in? Does it affect the structure of the protein in a significant way? Well, first of all, the change is that methane is converted into isoleucine. So recall that both methionine and isoleucine are examples of nonpolar amino acids. They have nonpolar amino acids, but the structures of their side chains are physically different. So when we're talking about a difference in structure that could potentially have an impact on the protein's ability to fold properly. So even though the polarity is not changing, right, the tertiary structure, the three dimensional structure of the protein could potentially change. But that depends on the role of methane in the original protein. So the mutation leads to an exchange of nonpolar amino acids, which means that the change is really only minor. Now, the exact effect is confirmed through experimental analysis, but we don't have access to that information. And so with that in mind, we've arrived at our final answer which reads, that the mutation leads to an exchange of nonpolar amino acids, which means only a minor change in the structure of the protein. And so with that being said, thank you so very much for watching. And I hope we found this helpful.

Suppose a mutation occurs in the DNA section in problem 17.89, and the first base in the parent chain, adenine, is replaced by guanine.
d. What effect, if any, might this mutation have on the structure and/or function of the resulting protein?

Key Concepts

Mutation

Protein Structure

Codon and Amino Acid Translation

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