Hey, everyone. So we're going to say that similar to transcription, the process of translation consists of three steps. We have our initiation step, our elongation step, and our termination step. First, let's take a look at our initiation step. Here within it, we're going to say we have ribosomes that consist of a small and large ribosomal subunit. We're going to say each subunit is made up of proteins and rRNA. So remember, rRNA is ribosomal RNA. Now we're going to say that the mRNA is going to bind to the small ribosomal subunit. So here we have our mRNA, and it's going to bind to this small ribosomal subunit. So here this would be a. Next, we're going to say for b, we're going to say that, methionine carrying tRNA, which has the anticodon of UAC, binds to the start codon which is AUG. So, here goes our mRNA that is bonded to the small ribosomal subunit. Remember, these are the codons, the three nucleotide sets that exist on the mRNA. tRNA, which is this large structure here, comes in and docks and pairs up complementarily with the codon of mRNA. So here's them pairing up. Here we see the hydrogen bonds that are forming between the nucleotides and nitrogenous bases involved. So this would be b. And remember, when we're talking about our nitrogenous bases, because we're dealing with mRNA, RNA in general, we're going to use uracil instead of thymine. Now, c, which is the initiation step, is completed when the large subunit joins the small subunit complex. So we're going to see here, we have our tRNA which has its anticodons paired up with the codons of mRNA, and now, we have this large subunit basically coming in and docking and pairing up with the small ribosomal subunit. Together, this represents our ribosomal complex. So ribosomal complex is the small and large subunits together. So this would complete our initiation step of translation.
Translation: Protein Synthesis - Video Tutorials & Practice Problems
Translation: Protein Synthesis Concept 1
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Translation: Protein Synthesis Example 1
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Which of the following is not a part of the initiation step of translation? Activation of tRNA through aminoacyl tRNA synthetase. Nowhere do we talk about needing to activate our tRNA when it comes to the initiation step, so this is our answer. If we look at our other choices, we have the combination of the large ribosomal subunit with the small subunit complex. This is actually the last step that concludes the initiation step of translation. So, this is a part of it. The binding of mRNA to the small ribosomal subunit is one of the initial steps in the initiation of translation. We need the mRNA to initially bind to the small subunit of the ribosome complex. The binding of Methionine tRNA with the start codon AUG through complementary base pairing is also a part of the process. Remember, mRNA comes in with its codon. Its start codon is AUG. A Methionine carrying tRNA comes in with its anticodon to match up with those nucleotides. So, yes, this is part of the process. Here, the only thing that is not a part of the initiation step of translation would have to be option a.
Translation: Protein Synthesis Concept 2
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Everyone, now we're going to take a look at the second step of translation, which is elongation. Here in elongation, a second tRNA approaches and binds to the next codon in the complex. Remember, we had our large subunit and our small subunit joined together to complete the initiation step. We had our methionine-carrying tRNA come and pair up with the codons of mRNA. Now, a second tRNA with another type of amino acid comes and docks in this second slot here. We're going to say here that a peptide bond forms between methionine (M) and the second amino acid, in this case, serine, and it passes.
Now, we have another event here. The second tRNA has docked in with its anticodon to pair up with the codons of mRNA. What happens now is this methionine is going to break off from this tRNA and come over here to help make this bond, this peptide bond. Now, this tRNA no longer has its amino acid attached. It no longer has methionine. What's going to happen is that we have translocation where the whole ribosome moves to the next codon after the first tRNA leaves the complex.
Basically, what happens is this whole structure, the large and the small subunits, are going to shift over to the right. Because here, this tRNA is empty now. We don't need it, so we shift the whole thing over. Now, here's this codon that was within the complex, it's now out here exposed. And we're going to jettison this empty tRNA. So this would be step f. This is translocation. The whole complex shifts over to this slot here, which has this growing peptide sequence going on. And what's going to happen is, over time, we're going to make that peptide chain longer and longer, adding more and more to it.
Now, here we're going to say steps d and f keep repeating. So we have another tRNA come in, the amino acid's going to break off and help to make the chain longer and longer. It keeps on repeating. Now, if we take a look here, this is just happening at one location, but in reality, a single mRNA can be translated by multiple ribosomes simultaneously. So here is our mRNA here and here's a ribosomal complex, here's another one. They're making these peptide chains, these sequences at the same time. So, we can make multiple peptide sequences at the same time off of the same mRNA strand.
Just remember, when we're talking about elongation, we're basically starting to add and chain amino acids together through these peptide bonds. This is the way the ribosomal complex works, where a new tRNA with a new amino acid attached comes and docks in next to the older one, in this case, a methionine-containing tRNA. And we're just going to try to make the peptide bonds to make our peptide sequence longer and longer.
Translation: Protein Synthesis Example 2
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Here, we're told a section of a protein has a sequence of Phenylalanine, Valine, and Arginine. These here represent our 3-letter codes. What is a possible mRNA codon sequence? To do this, we're going to have to utilize our chart here which gives us the first, second, and third letter codes for our codon. Remember, a codon is just a triplet of nucleotides, three of them together. Now if we take a look here, we need to find phenylalanine first. But remember that some amino acids will have multiple codons. If we look at this chart, we have it here and we have it here. And those are the only places. So we have to see where do we see these codes in our options here. Phenylalanine could be UUU, UUC, UGU, UGC. If we look at our options here, the only one that matches up with this chart is D, where we have UUU. But, let's verify the other amino acids. We have Valine here. Valine, if we look, where do we see it? Well, we see it down here (GUA). And then we have Arginine here. Where do we see it? We see it in more than one place. We see it here, and we see it here. We need AGA which matches up with this AGA. So, utilizing this chart, we find the amino acid and the three-letter code associated with it in terms of the codon. Doing that gave us D as our only answer.
Translation: Protein Synthesis Concept 3
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Hey, everyone. So in this video, we're going to take a look at the last step of translation, which is our termination step. We're going to say that translation terminates when the ribosome encounters a stop codon. Remember, your 3 stop codons are UAA, UAG, or UGA. In phase G, we're going to say the release factor protein binds to the stop codon. So, if we take a look here, we have our stop codon here, and we're going to see our release factor comes in and attaches. This will initiate phase G. We can see that we have a growing chain of amino acids connected together by peptide bonds.
We have our release factor protein that's attached to the stop codon. What's going to happen next is the peptide chain, the growing one, is going to be hydrolyzed and released from the last tRNA. So, we are going to sever this link here. And as a result of this hydrolysis, here is our released peptide chain here.
Next, we've released the peptide chain that we wanted to grow, so we no longer need our ribosomal complex. So, the whole complex just disassembles. So, we can see that our tRNA, which no longer has any amino acids attached to it, has broken off. We have our release factor protein that's broken off. We have our large ribosome subunit, as well as our small ribosomal subunit, they've broken apart, and then we have our mRNA chain right there that's just free-floating right there.
Now, this is important to know that methionine is generally removed from the protein backbone after translation. Remember, methionine is attached to the start codon AUG. So here we no longer need any of this. So everything is just broken apart, and this is the end of translation. We've created the peptide chain that we were looking to make. Right. So this concludes translation as a whole, the third and final step.
Translation: Protein Synthesis Example 3
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In this example question, it states, "Write the sequence of the peptide translated from the following DNA template sequence." Alright. So here, they're giving us this DNA template sequence. What we need to do first is we need to transcribe it into our mRNA. So here, this would be our 5' end and this would be our 3' end. Remember, since we're going from DNA to mRNA, RNA doesn't use Thymine; it uses Uracil. So our pairings would be A with U and still G with C. So since this is an A, this would be a U, this T would become an A, this C would become a G, and there goes our first codon. Next, we have CCA. Then we have UUU. Then we have CCA. So now we just have to find each one of these codons. So UA, and then C gives us tyrosine (TYR). So that means the answer is going to be either A or B. CC and then A gives us proline (PRO). So, so far they're the same. Next, we have UUU. So, UU and then U gives us phenylalanine (PHE). So, it looks like B is the answer, but let's just make sure that proline is the last amino acid here. So we need CCA, so CCA again, so again, it's proline. We had to transcribe our DNA template into mRNA because we needed Uracil, as Uracil is the nitrogenous base used within this chart. Once we decoded the mRNA codons, we can determine the amino acid attached to it. Alright. So again, that gives us option B as our final answer.
Tuftsin is an immunostimulator tetrapeptide having the following sequence:
Thr–Lys–Pro–Arg
Write a possible sequence for the gene (Informational & template strand) that codes for this tetrapeptide.