hello this lecture will cover transcription and translation as it relates to our DNA to RNA to protein so let's talk from the beginning um first we want to ask ourself how do genes determine trait so we know genes are going to be the instructions that our body gives us to give us the eventual characteristics that we have so genes are the genetic material in essence this is your DNA um and it's going to be the blueprint for an organism's characteristics so if you have um brown eyes if you are 64 if you have freckles all these things are going to be based off some instructions or genetic material that you have that tell you what you're going to be so these genes this DNA genetic material will be the backbone for building a polypeptide so if you remember that's the polymer for a protein a polypeptide those polypeptides will form primary secondary tertiary quatron structures to then give you a functional protein that's going to have some type of role or job in the cell we remember the shape of that protein structure is related to its function think of a wheel that has the ability to roll um so the protein is going to have a particular shape that determines its function and how it works in the cell and the protein will eventually give us some type of trait or characteristic right so once we have all of our proteins together that are working in your cell they're going to give you a trait or characteristic that is Meaningful to do what excuse me whatever your cell is designed to do so that's how we're starting right you have your DNA which is going to make your polypeptide that polypeptide will fold to create a certain structure um which has a function of your cell and then that's going to give you the freckles the brown eyes the 64 height so genes can be expressed um in two types of ways one is molecular function so that's going to be exactly how it operates on the protein level so you know molecule let's say it's supposed to produce um I sodium potassium right this is going to be what it does and then finally it can help to create a trait a phenotype which we'll talk about later so maybe you have brown hair maybe you have long nails all these things are going to be a trait or some type of phenotype um but there are also two different ways that genes can be expressed one which would be protein coding genes so these are going to be the genes in your DNA that actually make polypeptides so they're going to make the long string of primary structure needed to make a protein and then you have some other types of genes that are called non-coding rnas so these do not make any polypeptides Tides this is going to be very very critical to um just kind of protecting your DNA they don't really make a a protein itself but they're still going to be critical in um helping with the structure of your DNA itself so central dogma biology we talked about this um in one of the other modules before but I'm going to revisit this idea so DNA leads to RNA which leads to protein so we've already done the DNA replication piece we've already replicated our DNA right this is our DNA we've already done the replication process that's where we had leading and lagging strand but as we go from DNA to RNA this is going to be what we call transcription so the way I like to think of this is I like to think of your DNA is a big old recipe book um I'm probably spelling recipe wrong sorry forgive me so think of a big old recipe book it has a thousand recipes in it imagine you wanted to make sweet potato pie right if you wanted to make sweet potato pie you would take out the recipe card that is only for sweet potato pie only sweet potato pie recipe that is what going from DNA to RNA means you have a lot of information in this big recipe book but you want to take out just the message or just the RNA that you need to make that one recipe that's what transcription is transcription means writing it literally means writing so as we produce an RNA copy of the gene we want we call that an RNA transcript that's going to be like writing down that sweet potato pie recipe wonderful so now we have our sweet potato pie recipe from there we want to actually make the pie right the recipe is going to be words you know right and the p is going to be a product right it's going to be an actual item that we made a pie is much different than words that's exactly what's happening in Translation so translation or as we go from RNA to the protein that is called translation that's where we make our actual polypeptide that's where we make our product so the same way we were able to take our PI I'm sorry our our recipe and then make it Pi that's what we're doing here down in translation if you know what it means to translate something let's say you know how to speak fluent French and you can translate that to Spanish that's going to be taking something in one format changing it to another format so this is going to be the process of actually making the cake making pie um so make sure you're very familiar with DNA to RNA to protein the terms that we're using here what replication is transcription translation how they all play a role together that's really critical following That central dogma biology let's look first here in ukar Nots which is going to be here our more complex cell and then also in our procariota so UK carots have an extra step called RNA processing in which we can kind of modify that RNA a little bit um so that it can be active so I'm going to just walk you through what's happening to remind you your um DNA is going to be housed in your nucleus here you're going to undergo transcription so you're going from DNA to RNA you do have some RNA processing that still happens in the nucleus and then through that nuclear pore that we talked about before that mRNA is going to come out into the cytool in which it comes across a ribosome and it is translated so you remember how we always talked about ribosomes make proteins this is because it can take the message make proteins uh using that message okay um in procaryotes we don't have as much of a complex system because remember we don't have any organel so your DNA is present your DNA makes your RNA your RNA works with your ribosomes you get a protein so it's very very simple in bacteria um so again this is just reinforcing that idea the cytool everything happens there in the bacteria and then for UK carots it's the nucleus first then the cytool okay so let's talk about transcription for a bit um transcription is where we make that RNA copy of a gene in that RNA copy we call it an an RNA transcript so again DNA transcription RNA translation protein there are some viruses that can do reverse transcrip so that means they have RNA and they can go back to DNA but our normal flow is from left to right in this case so we can make a lot of different products from our RNA um and some of those rnas have very specific names which we'll talk about about each one um but the one that's most important for carrying that information is called mRNA that m stands for messenger RNA so with the transcription rnas let's talk about a few of them and what their goals are again mRNA is the messenger RNA this is going to be the one that actually has the recipe down or the message for making the protein so that's the one that says um you know has the code that we're trying to to transcribe that type of thing T RNA the t is used actually stands for transfer so the TRNA is going to help to carry the amino acids needed to translate that mRNA into polypeptides so what we're going to eventually do which I'll show you in a second is each of these little pairs we're going to pair them up with a specific amino acid right so we're going to pair those three up with a specific amino acid those three up and then eventually we'll link them together to form our string of beads that we've talked about in our protein days I hope y'all remember the necklace that I would talk about or use um so the RNA that is going to transfer or carry that amino acid to the MRNA or the message at the bottom that one is called TRNA Transfer RNA and then finally R RNA the r stands for ribosome and this is going to form the ribosome so the ribosome is essentially made up of R RNA and this is going to be where that transfer occurs so you see the big blue um ribosome in this image um we're going this is going to be where we're bringing together our code or our mRNA with our transfer rnas they're going to form a pairing which we'll talk about in a little bit um you see their complimentary pairing so a goes with u uh U goes with a G goes with c and all of these are going to pair together or bring together amino acids so that we can eventually form a long chain or a polypeptide of our amino acids so as we go from DNA to RNA right let's talk a little bit more about that process there's a few components on our DNA that are going to be critical as to how we start this process the first one is a promoter so a promoter is going to be where on the DNA we start our transcription process so we're trying to go from DNA to RNA a promoter tells us where to start think about a party or an event you've been to on campus you've heard of maybe a party promoter they're going to say hey Friday night this is where you want to be so a promoter on DNA is going to do the same thing it's going to show you where we are starting a Terminator is the end seeing the movie The Terminator you've heard of the word terminate or termination from a job or something this is going to be where we're stopping our code or stopping the transcription of our code and then finally you have some regulatory sequences they're going to be um towards the beginning before the promoter this is going to help us control whether we're making this mRNA or not so let's say um you don't want to make this transcript anymore you might have a big old protein that sits right here that blocks the transcription from occurring that's a regulatory sequence something that can sit here to block the party from starting think of like I don't know the fire department shutting a party down that the promoter said it's going to be at I whatever you want to think of and then finally the enzyme that's going to make the new strands of RNA is called an RNA polymerase don't confuse that with a DNA polymerase which replicates our DNA but this is an RNA polymerase so let's talk about this transcription process um as it relates to bacteria okay so as it relates to bacteria let's talk about it it's going to be a lot easier with bacteria we got three different steps we're going to cover throughout the process okay so the first step is called the initiation phase the very first one this is where we recognize where at we're going to start this entire process so this is going to include a special protein called a sigma factor which will first bind to the RNA polymerase and to the promoter sequence so the sigma factor is right here it's going to be um kind of the bridge between the promoter region on the DNA and the actual RNA polymerase think of like a primer for DNA polymerase and how that's necessary for the DNA polymerase to get on the Strand think of your Sigma Factor um as what is required to help the RNA polymerase get on the promoter okay so this is going to be a factor that's needed there um and again the sigma factor is going to help that RNA polymerase bind to that DNA sequence right we're taking our DNA and we're trying to make RNA from it this is going to create something called an open complex so this open complex kind of opens up the DNA strand so that we can make our RNA sequence from it um so then the next process is elongation okay so this is just as simple as a sound we're trying to basically make our mRNA transcript from our DNA so RNA polymerase is going to synthesize the RNA transcript during this process the sigma factor is released and your RNA polymerase will just slide along the DNA strand as it's sliding along the DNA strand it's using that DNA strand as a as a template so it's going to be the template that it needs to be able to make the RNA so I'm going to give you an example let's say DNA strand is um uh let's say a TT g c c right that's the template strand the opposite end of that DNA let's say just to keep give you some practice five Prime to three prime the opposite end of that DNA would be three down here five down here and our numbers would be something like um t a a c G G right so let's say we're using that top DNA strand that is going to be called our template strand the opposite DNA strand is called the coding strand so this one here would be the coding strand so remember DNA has two strands it's double stranded so the top one the one that we're trying to actually copy which is the top one this is going to be called our template Strand and the this DNA strand that goes along with that one is called called our coding strand um this is important because as we're making our new RNA right we're not replicating DNA in this process we're trying to make RNA that RNA strand is going to have essentially the same code as the coding strand but instead of uh T's we're going to have uh U's right so it would look something like this so if you see those are going to be the same strand except for the the U and the T switch there okay so I just want y'all to see that but even if you don't have the bottom strand or even if you have a problem like this where you just get the coating strand um you can either solve it by writing down the opposite DNA strand and then just making that simple switch here between the t's and the U's or you can just do your normal pairing between the template Strand and your new RN a strand making sure that you do not put any T's but instead you put U's so that's just a way to solve that problem if you ever get it um and you want to look through something like that okay so the final part of transcription here um is after we've done our initiation phase our elongation phase is termination real simple right so once the RNA polymerase reaches the Terminator or the very end right this is the very end of the RNA excuse me the D DNA strand the new RNA that we made is going to separate or dissociate from the DNA and we're left with this beautiful completed mRNA transcript um so the process is not too bad let me go back and just show you from the beginning everything we went through we had our initiation phase in which we had our Sigma factor that helps us buy to the promoter um in the RNA polymerase then the RNA polymerase will move down the DNA St to code this is just kind of showing you some of those terms we talked about template strand um coding strand all that and then finally once it gets to the Terminator it separates and you have your completed mRNA transcript okay so eukariotic transcription I'm not going to ask a lot of questions on it but I will briefly just mention it um it has very simple oh excuse me very similar features to Pro carots except we have a lot more steps so one big thing here is that um we have multiple types of RNA polymerase enzyme so for instance RNA polymerase 2 is going to actually transcribe the MRNA in RNA polymerase 1 and three this is going to make those non structural genes that I talked about earlier um mostly genes that are needed to make other molecules of rrna or TRNA we have to make them from somewhere they also need a code but RNA polymerase 1 and three will be respons responsible for that while RNA polymerase 2 is going to be what actually makes our our message RNA so our mRNA um also we're going to use a lot of transcription factors that help us say when we should start when we should stop again to reinforce that idea with RNA processing um once you have um bacterial mRNA we can immediately translate it and make the protein but it doesn't always happen in UK carot so I'm going to talk about about a few of the little things that happen in UK carots that make it different so that you're aware because remember we're more complex so our mRNA is usually a lot longer um and that longer mRNA is going to first be called pre-mrna so once we have our DNA up here the first thing we transcribe is an RNA called pre-mrna that's the first one here we're going to eventually cut and dice this thing up to make it functional but the first level is called premna so in premna you have two different types of um kind of um phases or two different types of areas one is called an Inon so this is something that we transcribed or wrote down but we're not going to make a protein from it then you have something called an xine which is something you you transcribe you wrote down but we're actually going going to keep it so in this picture the introns are um green so this is going to be the intron and then the exons are going to be yellow so there are more complicated reasons as to why we would write something down and not use it but as of right now I just wanted you to understand that there's some things you write down that we don't keep some things we write down that we do keep so the process of removing those introns is called splicing so I don't know if you've heard of the term splice but splice means to cut or chop or whatever so this is going to be the removal of those introns through throughout the splicing process we're going to go from something that has introns and extrons up here so it's going to be yellow and green we're going to cut it up and then we're going to eventually end up with our mature mRNA molecule that we're ready to have that will um be able to make the protein that we want there are few other modifications that we have called tails and caps which I'm going to mention in just a second so I want to show you here there's a five Prime cap and a thre Prime tail so what is a cap a cap is just um this modified um guanine that's attached to the five Prime end so to help protect your um mRNA think of like a bumper on your car your car has a front bumper and a back bumper the front bumper is going to be our five Prime cap um and it's going to be kind of this little methyl group it's right here really complicated I'm not going to have you identified or anything but it's going to be on the front part of your mRNA and this is going to be helpful for allowing that mRNA to actually leave the nucleus and go to the ribosome and then on the three prime end of that mRNA you have a polyat tail so this is going to be about 100 to 200 adenine nucleotides that are added to the three prime end of your mRNA MO molecule and this is going to be helpful because it increases the lifespan um and stability of your mRNA once it goes into cytosol you don't want it to leave the nucleus go into the cytool and then be degraded and then now you're missing some of the message that you had so this is a buffer in case they start eating away at mRNA it will start attacking it from this side and you'll still have a lot of space before you actually get to your code again this is splicing um don't worry about the details associ iated with splicing I'm not going to ask any questions with this so in your notes if you have them still in your notes you can definitely just cancel this out um this is another concept about splicing um it's called alternative splicing which just means if we have U four different parts so red yellow green and blue um depending on how we cut them up we can make different um proteins so if we just kept the red yellow and blue Parts you can make this red yellow and blue protein if we kept the red green and blue parts we can make a red green and blue protein so it's just talking about different ways you slice and dice the MRNA you can lead to different proteins okay so this concludes the transcription portion of the lecture um so I'm going to pause a little bit and I'll probably stop the recording now just to give you two separate um items to review