Central Dogma

in this video, we're going to do a quick refresher on the central dogma of molecular biology. And so recall from your previous biology courses that the central dogma of molecular biology casually refers to both the processes of transcription and translation. Now recall from your previous biology courses that the process of transcription is a process that will build an RNA molecule by using a DNA molecule as the coding template and recall that the process of translation is the process that builds a protein molecule by using the encoded messages of RNA. Now, as we move forward in separate videos, we will briefly refresh your memory on the process of transcription as well as the process of translation. Now, what you may not have known about the central dogma of molecular biology is that it only casually refers to both the processes of transcription and translation, but it directly refers to the uni directional flow or in other words the one directional flow of biochemical information from DNA to protein. And so in other words, what we're saying is that it is possible for D. N. A. To be replicated. It's also possible for RNA to be reverse transcribed back into D. N. A. But once the transfer of nucleic acid information goes to protein, this is an irreversible process or a one directional or uni directional process. And so if we take a look at our image down below, we can better visualize this and so notice on the left hand side over here we're showing you a DNA molecule. And so we know that D. N. A. Uh can be replicated. And so this circular arrow going from D. N. A. Back to D. N. A. Is just representing the process of D. N. A replication. Now, in addition to the D. N. A. Being replicated, we know that the DNA can be used as a coding template to build a molecule RNA. And so this arrow that goes forwards here from DNA to RNA uh is the process of transcription. Also this RNA could be used as a template to build a corresponding DNA molecule. And so that would be the reverse arrow going backwards from R. N. A. To D. N. A. And so this reverse arrow is going to be reverse transcription because it's the opposite of transcription. And then of course, we know that the RNA molecule can encode a message for building a protein and this is the process of translation. And so once again, the central dogma of molecular biology only casually refers to transcription and translation. However, directly refers to this uni directional flow of information here, this one directional flow of information. So notice we only have one arrow going from left to right from RNA to protein. And so once the information in nucleic acids has been transferred to a protein, this is an irreversible process and the protein is not going to be used as a template for building a corresponding RNA. That does not happen. And so this uni directional flow of information uh is what the central dogma of molecular biology directly refers to. And this applies to all living organisms. And so this year concludes our brief refresher on the central dogma of molecular biology. And as we move forward, once again, we'll get to talk a little bit more about transcription and translation to refresh your memories from your biology courses. And so I'll see you all in that video.

so later, in our course, we're gonna talk a lot of details about transcription, but in this video, we're just gonna do a quick review. So recall that transcription uses an enzyme known as our Nepal Emery's. And in our previous videos, we talked about how words that end in a sea tend to be enzymes. And our Nepal Emery's is an enzyme, and it's an enzyme that prelim arises or builds Arna, so the function of this enzyme can kind of be read backwards. An enzyme that builds Arnie and so RNA polymerase can build many types of RNA, including messenger RNA or mRNA, and the RNA molecules that are built by Arna Polyamorous are built in a specific direction, and that direction is from the five prime to the three prime end of the molecule. And it does that by aligning free RNA nucleotides to a DNA template, as we already know. And so our DNA molecules recall have the same exact sequence as the DNA coding strand, with the exception that all of the thigh means and the DNA are replaced with your cells in the RNA. And so let's take a look at our example below and quick secret. This diagram here is not nearly as complicated as it looks. And so we've got a DNA molecule that stretches across the diagram, and the DNA molecule has two strands. It's got a dark colored purple strand and a light colored purple strand, and these strands go in opposite directions. They are anti parallel and in the back, Uh, notice that we have this big pink thing. It's kind of hard to miss. That's the RNA polymerase. So this is the enzyme that's going to build our RNA, and the RNA polymerase has the ability to unwind the DNA, and we can see that here when it unwinds the DNA it separates the DNA coding strand from the DNA template strand, and the DNA template strand, which is down below here, is literally used as a template toe build the Arna and so free RNA nucleotides are aligned to the template and added to the three prime end of the Amarna molecule. And so the RNA is always going to grow from the five prime to the three prime end, and this RNA polymerase is moving in this direction and so noticed that on the back end the DNA is being rewound back into its original state. And so over here on the far right notice that this is a representation of the DNA molecule and the RNA molecule on the left. And so the dark colored purple strand goes from five prime to three, prime from left to right. And so this is a representation of that strand. The light colored strand goes from five prime to three, prime from right toe left, and so that's represented here. And the RNA molecule goes from five prime to three, prime from left to right. And so we're given the DNA sequence of the coding strand, and we have two questions. What's the sequence of the template strand and what is the sequence of the RNA strand? And so recall our base pairing rules. A is always pair with ts and Gs always pair with seas. And so when we apply that here, G's pair with sees a pair with teas and sees pair with cheese again. And so this is the sequence of our template strand. Now what's the sequence of our RNA strand? Is it gonna be the same as the coding strand or the same as the template, strand and recall. We've already said that the DNA molecule has the same sequence as the coding strand, with the exception that thigh means are replaced with your cells. And so that means that our our DNA strand down here is gonna have the same sequences are coding strand. So we're gonna have G g A. Except we're gonna replace diamonds with your cells and see. And so transcription is a fundamental process that occurs in every single organism. So it's good toe touch up on the basics. And our next video we're gonna do a recap on translation, so I'll see you guys in that video.

So you guys already know that translation is completed by ribosomes but recalled that there are also specialized RNA molecules called transfer Arnas, or T Arnas, that are also involved. And you've learned that ribosomes create proteins by reading the RNA strand and three nucleotide chunks called Code UN's. And these co dons are interpreted with a genetic coat and down below. We have a genetic code shown by this table and recall that t Arnas pair with amino acids and each of the TR nas contains a anti code on contains an anti code on that is complimentary to the code eons of the Amarna and so down in our example below. We're gonna use the genetic code to fill in the blanks throughout our diagram. And so notice in the back We have this big teal structure that we know is the right zone and ribosomes have a large any small ribs, almost sub unit. If this were a eukaryotic ribs own, it would be an 80 s rob zone with a 60 s large sub unit and the 40 s small sub unit. But if this were a pro carry attic ribs own, it would be a 70 s rival zone with a 50 s large sub unit and a 30 s small sub unit. So in addition to the RAB Zone, we also have an M r n a molecule and the purple and the Marne. A molecule has a five prime and a three prime end, and it also has a sequence, and the first three letters of the sequence correspond to our code On our first coat on which is a you g and up above, we have our t r ney molecule, and we also have to mawr tr nay molecules shown in these positions and notice that the TR nay molecules are associate ID and pair with amino acids that are shown up above. And in addition to pairing with amino acids, T Arnas also have an anti code on which are shown at the bottom of these tr Nas and the anti katanas recall pair and are complementary to the code eons of the M r n A. And so recall that the genetic code here uses the codename of the Amarna, not the antique Oden's of the T Arnas, and so recall that the genetic code, the first letter of the code on limits you to a specific row. Second letter of the code on limits you to a specific column and the third letter of the code on limits you to a specific position within the bloc. And so our first coat on is a you g. So a limits us to this row. You limits us to this column and to this block and G limits us to this exact position within the bloc which corresponds to a meth einen amino acid. And we could see that that's true that here we have, um, a thinning amino acid and that corresponds to an au g code on. And so notice that our rib resume is moving in this direction. So it's moving from the five prime to the three prime end of the M r N A. And so it's moving in this direction. And then here comes our T Arna that's making its way into this position and notice that our next coat on on the marina is you g g. And so, for the anti coat on use recall are pretty much teas. So they pair with ace so we can put in a here for the anti code on G's again pair with sees. So our antique Odin is gonna be a C C. Now again, when we use the genetic code, be sure that you're using the code eons of the M r n a. Not the antique Oden's of the t r n A. So we're gonna use you g not a C C. Now, when we use you u g I'm sorry, you g we get u G. And that's a trip to fan and we can see that that is true that here we have a trip to fan and the trip to fan correspond with a you g code on. So now the rivals, um, eyes going toe link the meth I inning and trip to fan amino acids to start creating a protein. And now, uh, the ribs own keeps moving. So now these t Arnas start to shift into the empty slots and eventually they'll shift out of the rhizome completely. So now here comes our next tr. Nay. Making its way to the ribs, Um, and notice that our next coat on is you use, See you, you see. And so again, use are pretty much teas and they pair with Ace. So here we have a a. G. Because these are the code aunts. And so now this is gonna make its way in here and again recall that the genetic code uses the code on of the Marne a not the antico tons of the tr in a So we're gonna use you, you see, and notice that you, you see, gets us final Alunan So up here we can put P h E for final Allan E And then again, this will also be connected to the chain of amino acids that continues to grow as t Arnas continue to feed it. And so again, what will happen is this end over here will end up being the end terminal end of the protein, Whereas the last amino acid that comes in, we'll end up being the C terminal end of the protein and recall it. Translation is a process that all living organisms do, and the genetic code is pretty much universal and applies to all living organisms, with some minor exceptions here and there. Now, in our next video, we're going to directly compare transcription and translation. So I'll see you guys in that video

in this video, we're gonna quickly compared. Transcription and translation transcription is in the left column and light blue, whereas translation is in the right column in light pink. So for the product formed, we know that transcription builds RNA molecules, whereas translation builds proteins. Now for the macro molecule change. We know that transcription uses DNA nucleic acids to build RNA nucleic acids, but we're still under the nucleic acid macro molecule category, and so, for that reason, we'll go ahead and put no here now for translation. On the other hand, we're going from RNA nucleic acids, two amino acids and proteins, so there's definitely a change in the macro molecule category now for the major enzyme or structure, we know that transcription uses are Nepal Emery's or an enzyme that prelim arises or builds Arna now for translation. On the other hand, we know that we use ribosomes now for the location of transcription. It's going to occur wherever the DNA is because the DNA acts as a template to build the RNA and eukaryotic cells. This is going to be the nucleus now for translation. It occurs in the cytoplasm of the cell. Now for the direction of synthesis. Uh, the RNA nucleotides, or the nucleic acid, is being built from the five prime to the three prime end. However, in translation, the protein that's being built is being built from the end to the C terminal end of the protein. And so this concludes our comparison of transcription and translation, and I'll see you guys in the practice videos.