Alpha-melanocyte stimulating hormone (α-MSH) is a 13-...

Question

Alpha-melanocyte stimulating hormone (α-MSH) is a 13-amino-acid peptide hormone responsible for pigmentations in hair and skin. Its peptide sequence is shown.

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c. Suggest a complementary template DNA sequence based on the mRNA sequence suggested in part b.

Accepted Answer

All right. Hello everyone. So this question says that Oxytocin is a peptide hormone involved in childbirth and lactation with a sequence of nine amino acids. Cyiqncplg suggest a complementary template DNA sequence that is used to form the Mrna sequence for this peptide. OK. So here on the screen, we have four different answer choices labeled A through D proposing different possible DNA sequences. And here after that, I went ahead and just wrote down once again the sequence of amino acids. So this is the kind of question where we're going to have to work backwards. That is we are given the amino acid sequence. So from there, we're going to produce our MRN A sequence and then our DNA sequence. So we are working backwards. Now, first, let's identify the amino acids and I'm going to use our three letter abbreviations. So C is cysteine cys, why is tyrosine Tyr I is isol, lucine ile Q is glutamine GLN and is asparagine A N C is cystine once more. So it's cys P is proline. So that's pr O L is lucine. So it's L eu and G is glycine. So that's goy. So from here, recall that during the process of translation, an MRN a coon that is a triplet of MRN A nucleotides codes for each amino acid that were given here. So normally you would reference your genetic code table to match each given code on to the corresponding amino acid. But because we're working backwards in this problem, the idea is instead to find a coon that would result in the amino acid that you are given. So again, working backwards now with this in mind, recall also right, that multiple different codons code for the same amino acid. And this is true of all the amino acids given here. So the idea is just to pick one code on from the multiple that are possible. So for the sake of simplicity, let's use the first code on listed for each amino acid. So for example, for cysteine, that would be let's see referencing our genetic code that would be UGU. So I'm going to write that twice because we have Sistine repeated twice in the sequence from there, we have tyrosine. So that would be uau once again, just picking the first coat on after that is isol lucine. So that would be a uu glutamine is CAA asparagine would be a au proline would be CCU lucine uu A and G for glacy. So at this point, it's important to recognize that even though we have the coons responsible for each amino acid given, that doesn't mean our MRN A sequence is complete because recall that during the process of translation, a start and a stop signal are necessary that is there has to be a signal to represent the start and stop of translation for that polypeptide specifically. So in addition to the coons that we already have for our amino acids, we have to add a start code on at the beginning and a stop code on at the end. So let's do that right. For the start code on that's going to be if you recall a UG and for the stop code on, we have a few different options. Examples of stop coons include UAAUAG or UG A. So for this question, let's just pick UA A and now our MRN A sequence is complete. So when it comes to MRN A, right on the left here is our five prime end and on the right is our three primate. So now we can work backwards from our MRN A to find our DNA sequence. So our complementary DNA sequence will be written from the three prime end on the left to the five prime end on the right. So in reverse, relative to our MRN A here, so to find our DNA sequence recall that A pairs with T U pairs with A because we're starting with MRN A as a template NC pairs with G and vice versa just for the record thymine also pairs with A. But here we are starting with MN which does not have a excuse me, does not have thy. So now let's go ahead and make our compliment starting off with a U its complement would be T ac the compliment of UG would be AC A UAU would be a T A. After that we have a UU which is ta a its compliment would be T A from there. We have C A which is G TT. After that, we have a AU our next code on was a AU. So its complement would be TT A. After that, we have UG which is AC A up next is CCU. So its complement would be GG A, then it's UU A, our next code on. So that would be A at in the DNA sequence last but not least or second last. We have G. So it's CC A and last but not least we have UA A whose compliment is att and there you have it. So with that final step, we have our complementary DNA sequence. Now, our DNA sequence would be running from three prime on the left to five prime on the right. And our final sequence is T AC ac A A tata A G TT TT A AC A GG A A ATCC A att. So if you watch this video all the way through, thank you so very much for doing so. And I hope you found this helpful

Alpha-melanocyte stimulating hormone (α-MSH) is a 13-amino-acid peptide hormone responsible for pigmentations in hair and skin. Its peptide sequence is shown.
SYSMQHFRWGKPV
c. Suggest a complementary template DNA sequence based on the mRNA sequence suggested in part b.

Key Concepts

mRNA and DNA Complementarity

Peptide Sequence and Codons

Transcription Process

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