welcome back friends in this series of videos we are going to talk about the DNA transcription process in details I find many videos in YouTube about DNA transcription but not many of them are detailed because if you are a bachelor student auto master students or if you are doing PhD you must know this C major biological process that is janie replication DNA transcription and the protein synthesis or translation so I am going to do all the video series about those three topics now in this series of videos I will be talking about the DNA transcription process majorly the DNA transcription in prokaryotes because I have already talked about the DNA transcription process in eukaryotes in different set of videos you can find them in the YouTube channel and you can just search for the DNA transcription of eukaryotic transcription in eukaryotes and you can see them now the thing is the transcription is a very very important event and it is a part of the central dogma of biology that is we have DNA DNA contains every information that is need to be coded or need to have but from the DNA the information should be transferred to some form which can actually work because DNA itself it is not working it is the master if they rule our whole body our whole cell by sitting there inside the nucleus so what DNA does actually it provides something some messenger to go there and follow the task that the DNA have to do and that those messengers are the RNA that we are going to talk about right so those RNA contain the information that are coded in the DNA does RNA we move from nucleus into the cytosol and then they will be translated into protein products now those proteins are the functional unit of our body they will do all the functions according to the law or rule of DNA according to whatever is written inside the DNA right so the thing is in this DNA transcription overview this video is about to be the overview of the DNA transcription and how we are going to talk about it in future videos this is going to be four videos this is the first one and then we'll be talking about the transcription initiation elongation and nation so the DNA transcription in prokaryotes is many way different than the DNA transcription in eukaryotes because generally the replication process in prokaryotes and eukaryotes and the protein synthesis in prokaryotes and eukaryotes are kind of similar but the transcription is a kind of different and the way it is different because you know in prokaryotic cell if I draw United here in prokaryotic cell prokaryotes and eukaryotes so if I draw them in prokaryotic cell what we can see here there are the genetic material whatever it is our DNA most of the time so that is present in the cytosol whatever genetic material it is let us say whatever genetic material it is present in the cytosol but in eukaryotes this genetic material is placed inside a different organelle and we know what it is it is nucleus and there we can find the DNA right so first difference is that the eukaryotic transcription occurs inside the nucleus but the prokaryotic transcription must operate in the cytosol right so for the eukaryotic system to work properly they need to bring all the nucleotides inside the nucleus and everything inside the nucleus to produce the RNA and when you're talking about the RNA owing DNA transcription or the production of RNA you are usually talking about the EMR in your messenger RNA because that messenger RNA contains all the code or photons who are translating to the proteins right so once the transcription is done once the RNA is made for example let's say this new thing is the RNA and that is produced both the case in in prokaryotes that RNA is the functional unit because in prokaryotes they do not have a junk element in their DNA whatever element whatever codon is present whatever code is present in the DNA that those all nucleotides code for a specific proteins right so all of these are kind of exons in function so those are na these RNA this mRNA is functional and it can translate into proteins but for the eukaryotic system the RNA that is produced or generating inside the nucleus is not mature RNA because the nucleus contains the chromosome and the DNA and all this DNA that is present in eukaryote itself only few percent of it is coding in nature that means only few percent of the DNA is coding for certain proteins rest of them are not coding for any proteins so the certain part which are coding for proteins that termed as exons and the parts that are not coding for proteins are termed as introns so the exams are the only functional you need so in the RNA we can find exams as well as introns so before taking it out inside the cytosol what this eukaryotic cell need to do is that they need to cleave all those introns out non-functional units out and only join all the exons together this process is called as RNA splicing or any splicing and this RNA splicing is required once the unex lifing is done then what we get with RNA with all exon sequences which are functional but that's not that because in this case also once you get that RNA that I only will be termed as premature RNE because in eukaryotes that are in it to be modified further how because let us say this is an RNA we have a five-prime group and a 3 prime group as usual now in the five prime terminal of that RNA they cap they put a cap that's called a five prime cap usually it is made up with guanine modified kind of going and also in the 3 prime section of the RNA they put a polyadenylation that is called the 3 prime poly 8a it's kind of a denial it in tail out there once this modifications are done inside the nucleus then only that RNA is ready to move out the nucleus and come into the cytosol and then they will be translated into proteins so the RNA that is produced you say the nucleus is premature the extra stage required in eukaryotic transcription is a maturation of the Dardenne after splicing as well as Phi prime capping as well as C prime polyadenylation in some other cases in some other eukaryotic system also there are certain modifications called RNA editing that may also result a lot of but that's not very common thing that's not very natural but these things are natural these things are these things must be done to make a mature RNA so once the RNA becomes mature then only that RNA will be translated into proteins and the translation will occur obviously the translation so the RNA we brought will be brought here and they will be translated into proteins so there are certain extra stages after transcription necessary for eukaryotic cells other than the prokaryotes okay so this is the difference big difference between eukaryotes and prokaryotes now if you want to know about more about the RNA splicing and RNA editing you know all these processes you can go to my youtube channel you will find videos on RNA editing and processing and everything about the details I will try to put the links of all this video in the description as well as hopefully if it's possible in a notation scene so let's let's see about so the transcription process that we are going to talk here is about the prokaryotes because you've already talked about this this eukaryotic transcription is far more complicated because more enzymes more factors are required but in prokaryotic system we only require certain factors certain enzymes for the process to offer properly so in prokaryotes in what we need actually like like all these cases another very important things you must know before starting with this process is that obviously like any biological processes like DNA replication transcription and translation we should require enzymes for the work right any biological processes we do require enzymes so the enzymes that are required for the prokaryotic transcription that we are going to talk here as well as the you carriers also that's called the RNA polymerase very common enzyme you probably heard this name a lot and usually we are going to talk about the polymerase type 2 9 a polymerase 2 okay so that is the enzyme usually used in the RNA I mean the DNA transcription in prokaryotes and alongside this RNA polymerase there are other some other factors that are also found in it prokaryotes and some more factors are found in eukaryotes right majorly eukaryotes this factor play a vital role and those factors are termed as transcription factors are simply designated as e and like the f1 key f2 TF 3 T 4 and so on they also have some detailed names but don't bother about that now the thing is once we have the RNA polymerase 2 as an enzyme to work as well as what we require is where a template or something with which they can synthesize this whole process so they require also the template thing okay so what is acting as a template to help them transcribing the DNA into our because remember the difference between DNA and RNA is the DNA is double-stranded RNA single-stranded and the DNA contains the bases cytosine uracil thymine and adenine but on the other hand instead of the thymine RNA contains uracil okay so so in RNA instead of climbing that is the difference otherwise it's kind of same because the you receive the chemical property of uracil is kind of similar to chemical property of thymine so that they can pair same type of bonds between adenine only so now the most important thing and I found many students have problem with this particular region so very much carefully let us say there are two strands of DNA right let us plot both the strands here these are the two strands of DNA one strand let us say five 23 prime the opponent form will be like that so two different strands are present in DNA double stranded DNA now there is a question that we only need to produce one strand as an RNA so which DNA strand we will choose to have as a template to produce another string and the answer lies upon the directionality of this process because you know the process like DNA replication transcription or translation they have a pair directionality it should not go back and forth never it has a particular direction to go Apolo so the directionality here in DNA transcription just like the replication the directionality here is PI prime to 3 prime this is the directionality required for the process of DNA transcription in prokaryotes okay so now think about it the directionality 5 prime to 3 prime means the RNA chain that will be synthesized will be from 5 prime to 3 prime it does not mean it will follow the 5 prime to 3 prime of the DNA it means that the RNA chain that is going to be synthesized they will be synthesized from 5 prime to 3 prime right so if we take this trend as a template this 5 prime to 3 prime DNA strand as a template and start transcribing in this direction in that case we need possible to synthesize five prime to three prime RNA transfer is no because this is if this is the way we start this should be the three prime of our RNA and we are going three to five Prime and that is not allowed that is not possible so this is not the possibility so what is the possibility is using this strand because if we start using this blue strand here of the DNA as a template then it is a possibility of transcribing five prime to three prime of our new RNA sequence and that is how they actually work this is the directionality right so in this particular picture they can use this blue strand as a template right so the blue strand here acts as a template DNA strand so once you figure out what is the template DNA strand it is fairly easy to conclude what is the other DNA strand will be called the other DNA strand is usually called as the complementary strand of the template right the complementary strand of template because you know if the template is from 3 prime to 5 prime so obviously the other complementary of the template strand will be from 5 prime to 3 prime and thus we can see so the strand here is called Kali as coding strength any mask why coding we know why it is called template strand because it is acting as a template but now remember if our RNA is using this as a template strand and synthesizing the RNA from 5 prime to 3 prime let us assume that it is synthesizing up till like that the DNA the RNA is going to generate should have the same sequence the similar sequence like this 5 prime to 3 prime other strand because this 5 prime to 3 prime star is complimentary to this C prime to five prime and our RNA is also complimentary to three prime to five prime that means the our RNA and these are the strand are same same component of the genetic material right now if I give you another small example you can understand very quickly sorry let us say let us say in the top five prime to three prime a t TG g CT a for example let us say this is the strand this was the strand now the opponent strand here the other strand the complementary strand of this da we should have you know T a a c cg 8 t right v prime ministry plate right so this is remember this black one is coding we are calling it coding this blue one we are coding calling it template right so now the third strength that is our RNA strand RNA is taking this blue one this template as a template so the RNA strand that is going to produce the complementary of the template so the T definitely the complementary will be a if there is a in RNA we have you again you remember in RNA it will be uracil instead of thymine and in C we have G is C Q a and that's it so now just compare the two sequences this coding DNA strand with the RNA sequence what you will find a a TT you you when en you is the same so G C so this two sequences you can see are the same so as the sequence of RNA is same like the opponent complementary sequence of the template DNA that is why the Strand is called as a coding strength because ultimately the RNA these are this will be a code with three nucleotide sequence will be food right so the RNA sequence is acting as a coding actually in our body and the DNA which is having that kind of sequence already in are called as a coding DNA strand so this is a very important concept and seeing many people to make mistake in this particular area so simple idea try to memorize CT just CT two strands C upper one t nor and T is the template template is the strand which is used by RNA to synthesize the whole RNA an opponent was the pudding why because it's same with the RNA sequence that's it that is very simple right so once you know all these things about the DNA transcription overview how this whole process will work now the whole process of DNA transcription will work let me give you a brief overview of this whole process the overview of DNA transcription works like something like this let us say let's say we have this DNA now we have two different strands remember we have this coding strand as well as we have this template strand right so we have this time so five prime three prime and right so we have this so let's let us assume that we are drawing it very simply s why I am drawing it planar two-dimensional structure because I cannot do a three-dimensional structuring a board which is also a two dimensional place here find this image now in this case if this is a coding and template strand that is present the step-by-step process of gaining transcription in very basic overview is that there will be the presence of the enzyme RNA polymerase 2 so RNA polymerase 2 RNA polymerase 2 will come it has a multi small I mean subunit complex right so this RNA polymerase 2 will come and join and that RNA polymerase 2 will actually attach with some region of this DNA stand I mean gayness sequence some region and it binds with both the strands of the DNA does not mean that it will only bind with the template it binds with both the strands of the DNA right in a distance location somewhere in a particular location and this binding of RNA polymerase to in a particular location in the DNA it depends on a specific sequence that is present in the game and that sequence is called as consensus sequence consensus sequence so once it is attached to the consensus sequence sty loosely in that case that loosely bounding content is stabilized by another factor that is associated with RNA polymerase 2 and that is called Sigma factor so Sigma factor joins in and will stabilize this whole process will stabilize the attachment right so let me draw the RNA polymerase here let us say this is the polymerase and the Sigma factor is in green here so it is added and the structure is kind of stabilized now so once the structure is stabilized and the attached to particular consensus sequence after binding of the Sigma factor they scan for a particular sequence they just scan for the sequence so the sequence scanning is going on right to the start site because you know in the DNA there are particular sequences that is telling this RNA polymerase that this is the time to start transcribing the DNA and those sites are called as promoter sites so once the RNA polymerase in the place of a right promoter sequence the Sigma factor will move right they will scan for the DNA and move towards a particular direction here let us say this is a particular promoter site we need to look for so once they reach this promoter site once they reach this promoter site in that case Sigma factor will be dissociated so the Sigma factor now we are coding region let's say here it is Sigma factor now dissociated the this RNA polymerase 2 is in the promoter place now their RNA polymerase along with some other factors are sometimes itself start to melt that DNA in that particular area promoter start melting now the first complex form is called the closed complex and start melting the deme once the DNA start melting is start to form which is called a bubble like structure see if we form something like this so let's let's street forms formation of a bubble like this this kind of have a bubble like structure form and the polymerase is now still attached with this particular area let us say this is this is the polymerase bubble like structure form after this formation of bubble like structure then they will start adding all those ribonucleotide sequences RNA nucleotide sequences will there and those nucleotide sequence need to start adding in this position let us say in this template you start add that and start producing the RNA sequence from 5 prime to 3 prime of the RNA sequence production ok so this is how the elongation we work now the sequence of nucleotides sequence will be added one after another polymerization we take place and they create a chain of RNA so they start creating the chain of RNA sequence there so after this production is done they will do all this elongation for process something and unless they will heat another particular sequence present in the DNA and that sequence is a kind of termination signal sequence right and the termination can be of two different type one is called the Road dependent termination other one is a row independent termination or intrinsic termination so for the road dependent termination what will happen there is a protein called raw protein which is a hexameric protein by the way that means it has six different unit subunits so that row protein will come and the row protein will be here will be attached with the growing RNA chain it is not a test annual their row is kind of a Kelly case you know the DNA replication the row is kind of a helicase just a similar structure like helices and it can actually dissociate a DNA and RNA hybrid so it will just launch itself and then it will drag itself towards the top of the RNA synthesis and once this ro factor we reach at this particular point let us say the row reaches here and leaving this region you can see this there is a formation of this dna-rna hybrid and the row can actually dissociate this dna-rna hybrid strong each other and the RNA will not fall off right that is how row dependent processes work in row independent process what happens actually healing the production of RNA in the are any internal sequences for example RNA is now producing the army internal sequences there are more of a GC v reach GC rich content and GC reach palindromic content palindrome means a particular structure which can fold and form a loop between themselves for example in this particular structure you can see two G's are placed here and cruces are placed here similarly if this folds back they can form easily they can here form a loop something like this the formation of loop takes place there as well as it is followed by followed by somewhere poly you stretch with the adenine sequence of the DNA this is the DNA situation just focus on this particular area you can find something like this that itself they are having poly G and CS and they form a pairing wrong they form a loop and followed by a poly you stretch in the DNA it is paired with poly you stretch in the RNA obviously then it is paired with the DNA means so in that case a you is a very weak force but GC is a very strong force so the difference in the force combinations there will just rip off the RNA from the DNA take the RNA out this is the intrinsic termination signal why it is intrinsic because the signal which is a GC rich signal is placed in the RNA itself okay so this in a sense is the overview of DNA transcription we break it down in three sections for our understanding like the initiation elongation and termination right so the three stages initiation then elongation and then termination from the next videos onward we are going to talk about each of these different sections initiation elongation and termination process in details so if you want to study in details please stay tuned and watch the rest of the videos