Understanding DNA Transcription: A Comprehensive Guide
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Introduction
Welcome, Ninja Nerds! Today, we dive deep into the fascinating world of DNA transcription. Understanding how DNA is transcribed into RNA is fundamental for grasping basic biological and molecular processes. This article will break down DNA transcription, the enzymes involved, the differences between prokaryotic and eukaryotic transcription, and the various factors regulating the process.
What is DNA Transcription?
DNA transcription is the process of converting DNA, specifically the genetic code, into messenger RNA (mRNA). In simple terms, transcription is crucial for gene expression, enabling cells to produce the proteins required for various functions. This process occurs in both prokaryotic and eukaryotic cells but varies in complexity:
- Prokaryotic Cells: Simple and utilizes a single RNA polymerase enzyme.
- Eukaryotic Cells: More intricate, requiring multiple RNA polymerases and transcription factors.
The Fundamental Steps of Transcription
To understand transcription thoroughly, we need to explore the main stages involved: Initiation, Elongation, and Termination.
1. Initiation of Transcription
Initiation is the first crucial step in transcription. It begins when the RNA polymerase binds to a specific region on the DNA called the promoter. The promoter consists of distinct nucleotide sequences vital for RNA polymerase recognition and binding. Below are the critical components involved:
- Promoter Region: Recognizable sequences in DNA where RNA polymerases attach. Examples include:
- Prokaryotes: -10 (Pribnow) and -35 regions.
- Eukaryotes: TATA box, CAAT box, and GC box.
- RNA Polymerase: The core enzyme dedicated to synthesizing RNA.
In prokaryotic cells, a single RNA polymerase binds to the promoter using a component called the sigma factor to facilitate this binding. Conversely, eukaryotic cells utilize several proteins called transcription factors in addition to RNA polymerase.
2. Elongation
Once initiated, RNA polymerase moves along the DNA strand, reading the template strand complementary to the coding strand. Several key points on how elongation works:
- RNA polymerase synthesizes RNA in a 5’ to 3’ direction while reading the DNA in a 3’ to 5’ direction.
- Newly synthesized RNA strands are complementary to the DNA template.
- The elongation rate in eukaryotes is generally slower than in prokaryotes due to their more complex transcriptional regulation.
3. Termination of Transcription
The termination phase signals the end of transcription, allowing RNA polymerase to release the newly formed RNA strand. There are significant differences between prokaryotic and eukaryotic organisms:
-
Prokaryotic Cells: Termination can happen via rho-dependent or rho-independent mechanisms. In rho-independent, sequences in the newly formed RNA trigger the formation of a hairpin loop causing RNA polymerase to dissociate.
-
Eukaryotic Cells: Termination involves specific termination sequences leading to the cleavage of RNA, often followed by the addition of a poly(A) tail, a string of adenine nucleotides, on the 3’ end of mRNA for stability and export from the nucleus.
Differences Between Prokaryotic and Eukaryotic Transcription
Prokaryotic Transcription
- Simpler process; uses a single RNA polymerase holoenzyme.
- Transcription and translation can occur simultaneously because there is no intron/exon structure or compartmentalization.
- One type of RNA polymerase produces all types of RNA (mRNA, rRNA, tRNA).
Eukaryotic Transcription
- More complex; involves three different types of RNA polymerases (I, II, III).
- Requires several transcription factors for the binding and initiation process.
- Involves post-transcriptional modifications, including 5’ capping, 3’ polyadenylation, and splicing of introns.
Gene Regulation and Transcription Factors
Gene regulation plays a vital role in the transcription process. Specific sequences in the DNA, known as enhancers and silencers, can affect the transcription's rate:
- Enhancers: DNA sequences that increase transcription efficiency when specific transcription factors bind.
- Silencers: Sequences that can slow down or inhibit transcription.
Specific Transcription Factors
Transcription factors are critical for determining whether a gene is expressed. For example, in eukaryotes, general transcription factors help in binding the RNA polymerase to the promoter region, while specific transcription factors enhance or repress transcription.
Post-Transcriptional Modifications
Once mRNA is synthesized, it undergoes several modifications to produce a mature mRNA strand ready for translation:
- 5’ Capping: A modified guanine is added to the 5’ end to protect mRNA from degradation and assist in ribosome binding during translation.
- 3’ Polyadenylation: Addition of a poly(A) tail that stabilizes the mRNA and allows for the export of mature mRNA out of the nucleus.
- Splicing: Removal of non-coding introns and joining of coding exons to produce a functional mRNA
Alternative RNA Splicing
One fascinating aspect of RNA processing is alternative splicing, which allows a single gene to code for multiple proteins, enhancing genetic diversity and function of the resultant proteins.
Conclusion
DNA transcription is a complex yet beautifully orchestrated process essential for gene expression and, ultimately, protein synthesis. Understanding the intricacies of transcription, from the role of RNA polymerases and transcription factors to the differences between prokaryotic and eukaryotic systems, equips you with vital knowledge of molecular biology. As always, if you enjoyed this breakdown of DNA transcription, don't forget to like, comment, and subscribe to our channel for more engaging content!
Stay curious, Ninja Nerds!
transcription before we get started if you guys do like this video please hit that like button comment down in the
facebook instagram patreon all that stuff will be there all right ninjas let's get into it all right ninja
so with dna transcription we have to have a basic understanding of just the definition what the heck is
and converting that into rna so it's taking dna and making rna that's all transcription is
but in order for transcription to occur in order for it to take place we need two particular types of proteins
or enzymes if you will to facilitate this process and i want to talk about those real quick
because these are very important now transcription can be kind of different okay and it's important to know the
dna strand on this dna strand we have these blue portions that i've highlighted here as a
box with some lines in it this right here for right now i want you to know is what's called a promoter so
to bind onto the dna and then start moving through the dna taking the dna and making rna so that's
the first thing you need to know is within the dna there's a particular nucleotide sequence
we'll talk about a little bit later called a promoter region and that's the first thing that we need to
identify let's say that we take this particularly for prokaryotic cells so prokaryotic cells
and we'll just say like a bacterial cell okay prokaryotic cells use a very particular type of enzyme what
rna we're going to put poll polymerase holo enzyme now that's a lot of stuff let me explain
what this is and i'll show you the structure of it a basic structure of what the rna polymerase holoenzyme is
it's made up of two things one of the components of this enzyme is called the core enzyme
and the core enzyme for this rna polymerase holoenzyme consists of multiple subunits that they
two beta units technically we say beta and beta prime if you really want to be specific and
the core enzyme which makes up rna polymerase what's important to remember is that these are what are going to
and makes rna the next component of the rna polymerase holoenzyme is the portion that we need in order to bind
to the dna to the promoter region without it we won't be able to allow for this rna polymerase to bind to the dna
subunit or factor if you will okay these two components the core enzyme which is made up of the two alpha the
entire rna polymerase now let me show you for example here let's say i represent the core enzyme
subunit as kind of like a pink circle with some lines in it right so let's imagine here
we have that core enzyme which we're going to represent like this and then the other component of it which
bind to the promoter region once it binds to the promoter region then this core enzyme of the rna
this dna and as it moves down the dna it'll read the dna from three to five and synthesize an rna
prokaryotic cells with the rna polymerase holoenzyme is very different from eukaryotic cells
in prokaryotic cells that mrna that we made from this one rna polymerase holoenzyme can make all the mr
rna within the prokaryotic cell or t rna within the prokaryotic cells so that's very important big thing i
polymerase which is called a holoenzyme made up of two components a core enzyme made of these subunits
and a sigma subunit the core is what reads the dna and makes the rna the sigma subunit is what
all the rnas within that prokaryotic cell in eukaryotic cells it's a little bit different
so let's talk about that let's say here we have three promoter regions that i want us to
two different things in order to allow for transcription to occur and this portion here right and this
a particular enzyme an rna polymerase and a transcription factor let's let's kind of write that down
so let's say that we take this first promoter we want to read this gene this portion of the dna
and make rna and this is the rna that we're actually going to synthesize right here okay from this
gene a particular enzyme let's represent this in blue since we've been kind of doing
and make this rna there's a particular enzyme what is that enzyme called it's called rna polymerase
but this is the first promoter within the eukaryotic cells that we're talking about right
so let's call it rna polymerase one rna polymerase one will read the dna and make a particular type of rna but in
order for it to do this it needs a special protein that can bind to the promoter region which allows for
the rna polymerase to bind to the dna and read the dna what is that particular protein that
what is this called this is called a transcription factor tf and there's many different
types of transcription factors the particular thing that i need you to remember for right now
two things i need in order for this rna polymerase to be able to read the dna and make this rna rna polymerase 1 needs
the rnas within prokaryotic cells from one rna polymerase but rna polymerase 1 makes a very
is incorporated into what's called ribosomes ribosomes and ribosomes are utilized in the translation process
pretty easy from this point here's another promoter region of a particular sequence of dna
right within a eukaryotic cell so this is the second promoter region another enzyme binds another rna
a set of general transcription factors to bind to this promoter region so general transcription factors we need to
read it and then make what make these particular types of rna we have here this is well this was the first promoter
2 rna polymerase 2 will bind to this promoter via the transcription factor read the dna and make rna what kind of
rna mrna you'll see later again is the component it'll have to go through some very specific modifications
okay the other thing that you guys can remember if you guys want to be scholarly or ninja nerdy
there's another rna that's made here and we'll talk about it a little bit later with what's called splicing
and these are called small nuclear rnas and these are involved in what's called splicing and we'll get into that a
little bit more in detail later okay but big thing rna polymerase ii with the help of general transcription factors
sequence of dna within this eukaryotic cell is going to make trnas and it's the same process what do
and then synthesize what rna what type of rna is it making the type of rna that is being synthesized from
also made by rna polymerase type 3. and if you guys really want to be extra ninja nerdy technically
even a teensy bit of rna is also made here as well okay now trna what the heck does this do
process and we'll talk about that in a separate video so i know this was a lot of stuff to
t rna these are the big things that i want you to take away from all this if you want to go the extra mile be extra
go the extra mile technically three can also give way to rrna but this is the basic thing to take
away from what we just talked about and then the other thing is in prokaryotic cells we don't need all of
you notice in eukaryotic cells that we have particular transcription factors that are going to be needed for each rna
is the sigma subunit because it's the portion that's binding to the promoter to allow
the core enzyme of the rna polymerase to read the dna okay so that kind of covers the basic
to occur now there's one other thing that i want to talk about very quickly before we really
start talking about mrna because that's going to be the primary topic here i want to have a
speeding it up or slowing it down okay so the next thing i want to talk about is very very briefly
on eukaryotic gene regulation so i want to have a quick quick tiny little discussion on gene
easy and it kind of makes sense along with what we're talking about but we're not going to talk about it in
prokaryotic cells we're primarily going to talk about this gene regulation and eukaryotic cells we're going to have
particular sequences of dna particularly palindromic sequences which are called enhancers and enhancers
are basically dna sequences and the big thing i want you to take away from this they can increase
transcription okay we'll talk about how they do that the other thing that can regulate the
in silencers they do what they decrease the transcription rate or the transcription process
now it's really straightforward it's relatively simple let me explain what i mean let's say here we have a
strip of dna we're going to explain how this happens so here's our strip of dna and remember this blue region what did
we call this blue region that we talked about above this was called our promoter region and
do you guys remember let's take eukaryotic cells in this case what we needed in order for this process to
and then what else did we need in order for that to read the dna and make rna you needed a particular rna polymerase
now this is going to go read the dna this rna polymerase will read the dna and then make rna right now here let's
say that we have the promoter and you can have this enhancer upstream from the promoter or it could be down
here regardless of where it is it's usually can be close to the promoter or it can be far to the promoter so you're
influence a promoter that's all the way down here how that does it do that there's particular structures there's
really deep into talking about specific and general transcription factors the general transcription factors are
what bind to the promoter region specific transcription factors which we're going to really kind of do a
different color here let's do purple specific transcription factors will bind to this enhancer region so
this let's put specific transcription factors these will bind to the enhancer when they bind
the enhancer it causes the dna to loop in a way that it's in very close proximity to the
promoter region even though it's far upstream from it and then what was bound to this promoter
polymerase so now that these are in close proximity guess what this general trans this uh specific
enhancers can be either far upstream or far downstream which makes it hard to interact with the promoter
bringing it in close proximity which can then stimulate the specific transcription factors and the
what do you think silencers do the exact same process we're not going to go into detail of it
but if you imagine i did the same thing i put the silencer here and i have a specific transcription
factor that bound here it's going to fold it in a particular way bringing it close to the promoter
inhibiting that promoter region and slowing down the transcription process it doesn't make sense it's pretty cool
too right so i need you guys to ask yourself the questions because we're going to talk about these
these general transcription factors what in the world are these specific transcription factors
you guys know when we make a protein whenever we have like a cell signaling response we've talked about
tsh which stimulates thyroid hormone synthesis right tsh will act on a particular receptor we call these
g-protein-coupled receptors right like g-stimulatory proteins those g-stimulatory proteins will
protein kinase a protein kinase a depending upon what type of you know transcription factor you need in this
that'll be needed to bind to the enhancer change the shape of it activate the promoter have the rna
and so you'd have this get read you'd make an mrna that would then get translated and make
thyroid hormone doesn't that make sense how that process occurs so we can increase the transcription and
testosterone does what testosterone will move across the cell membrane it'll bind onto a
intracellular receptor when testosterone binds onto the intracellular receptor what will that intracellular receptor do
bind to the enhancer when it binds to the enhancer loops it brings it close to the promoter
right that's the whole process of how we increase transcription and the same thing would
happen if we wanted to decrease it just we would have some type of repressing transcription factor binding
to the silencer that would inhibit the transcription process so i think we have a pretty good
idea now of the basic concepts of eukaryotic gene regulation now spend most of our time talking about
the transcription particularly of mrna all right so when we talk about transcription we've had a basic concept
of it right that we need rna polymerases and transcription factors to read the dna and make the
rna but the real one that i want us to primarily focus on which is primarily important with
transcription of dna is mrna that was the real important one now that's in eukaryotic cells with
rna polymerase holoenzyme so what i want us to do is i want us to go through particularly and more d we already have
the first stage that is involved here is called initiation of transcription so the first step that
we have to talk about is called initiation of transcription now this is the part that we've pretty much already
okay that we're going to do initiation with we're going to have our prokaryotic cells here
on this left side of the board and then over here we're going to have the eukaryotic cells here on the right
side of the board what i want us to do is to have kind of a comparison a side-by-side comparison
of the initiation process the first thing that we need to know is we've talked a little bit about this
already but this blue region what did we call this blue region here again this blue region was called the promoter
sequence that is very very specific and allows transcription factors and rna polymerases to bind to the dna
it's kind of a signal if you will it's like hey here i am come bind to me in prokaryotic cells the promoter
which means from the start point at which the rna polymerase starts reading the dna and making rna
if you go back 35 nucleotides that's kind of the point at which the rna polymerases will
but they wanted to give this one a name so they called it the pribno box just meaning that it's negative it's 10
nucleotides away from that startup transcription right and then the last one here is called the
plus one region which is also called the transcription start site so it's going to be pretty
these are called the top box which means that you would have thymine adenine thymine adenine
nucleotide areas at which the rna polymerase is type 2 and transcription factors will bind to
that is the important thing okay now the next thing here is the polymerases the rna polymerase is
within prokaryotic cells it's just one it's rna polymerase holoenzyme right we already kind of
the sigma subunit all of that's needed to bind to the promoter region and eukaryotic tells us a little bit
more right we said that we needed two things we needed an rna polymerase and which what are we making here
initiation and we're going to say that we're trying to make what we're trying to make mrna transcription
so we're doing transcription but we're making mrna so what was the particular rna polymerase
1 2 3 r m m is for r for the mrna so rna polymerase type 2 is one of the things that i need
the second thing that i need is the general transcription factors and there's just so many of these that i
don't know how important and how specific we really need to go into these i'll give you some of them but i just
want you to know that there's so many different types of them the main one if you had to remember
2 d this is the one that i really want you to remember and the reason why is this contains a structure called the
transcription factors and you can remember these by transcription factor 2 and there can be h there can be e
so i don't know how important it really is to know that but the main one i want you to remember
is the transcription factor 2d all right so these are the things that we need in order for initiation to occur
so let's take for example we're going to have on one side eukaryotic cells will the eukaryotic
enzymes will bind and on this side the prokaryotic will bind right so let's say here we take for
and we'll make the rna polymerase over here for the eukaryotic cells just for the heck of it
we'll make it orange okay just so we can distinguish the difference between these so what will happen this whole rna
subunit of it the sigma subunit and if you really wanted to go back you guys remember we made that pink
okay for the eukaryotic cells what do we need we need the rna polymerase type 2. we said we're going
type 2 and then what else do we need we need those general transcription factors there's a
transcription factor 2 d which contains the tata binding protein so it binds to the tata box which is the
promoter region in the eukaryotic cells then allows the rna polymerase 2 to bind to the dna
now once the rna polymerase is bound to the dna it's going to start moving down the dna strands reading it
and making rna so we've now started the process of transcription that's all that's
we'll put rna polymerase and we'll put h for the holoenzyme and for that one up here this is going to be
rna polymerase type 2 right once this is bound and it's in the dna it's going to start
reading the dna as it reads the dna it'll make mrna that process by which it does that is called
the mrna now within elongation a couple different things happens and this is thankfully the same in
prokaryotic cells and eukaryotic cells so thank the lord for that right so let's just say that we take
either one of these rna polymerases let's just for the heck of it we'll say here's your rna polymerase ii okay
here's your rna polymerase two and it's reading the dna the dna we already know has two strands
we're going to call this top strand here this top strand sonogram this top strand up here we're going to call this the
now when rna polymerases read dna the strand that they read is the template strand or the antisense strand
so that's the first thing i really need you guys to remember is that the rna polymerases
what strand do they read they read we're going to put the template strand or also referred to as what else
the antisense strand and that's the strand that they use to make the mrna they do not use the coding strand
so let's kind of put a little asterisk here that this is the strand that we're gonna read
now when it reads it it does it in a way that you guys if you guys watch our dna replication video this should be
so darn easy let's say here this end of the dna is the three prime end that means that this end is
on this side should have a complementary anti-parallel strand on the other side which means that this is the three and
and then opens up the dna who opened up the dna before it was that whole in replication it was that whole like
replication complex rna polymerase does that so the first thing we need to know is that rna
you opened the dna and you had those single stranded binding proteins which keep it stable and kept it open right
stranded dna molecules right so it stabilizes the single strands then what was the enzyme in replication
that opened up to unwound the dna helicase rna polymerase has its intrinsic helicase activity so it also
so let's say here as it reads the dna in this direction three to five it'll make mrna
that'll be going in the opposite direction so it's going to read this 3 all the way to the 5 direction and as it
does that it starts synthesizing mrna right and this mrna will be synthesized in what direction
the three end so we know the next thing that the rna polymerase does whether it be in prokaryotic cells or
said that in replication the dna polymerases read the dna and then if there was an accident or a
mistake they would proofread it and then cut out the nucleotide what about rna polymerases do they do
that as well because it looks like they've done everything that was similar in dna replication
that's the one thing that's controversial so the only thing that's kind of relatively controversial
is is there a proof reading function we don't really know it's still subject to study
so that's one thing to remember if you want to compare this the proofreading function is somewhat
read this dna and we've made rna i know we talked about this a lot in dna replication we're talking about it here
and sometimes it really can be confusing when you're saying five end three and i don't i don't i
don't freaking get what you're talking about zach so i want to take a quick little second
and explain what the heck i mean when i say it reads it from three to five and synthesizes it from five to
three a diagram i really think will clear this up for you let's take a second to understand what i
it's really important to understand that so let's say here we have this strand of dna so this is
side the blue one and then this is going to be the rna that we're going to synthesize utilizing
the rna polymerase type 2 and eukaryotes are the rna polymerase hollow enzyme and prokaryotes
it's the oh so this is going to be the three end what's the five end it's the phosphate
starting at the o h portion towards the five end where the phosphate is so the rna polymerase let's pretend i'm the rna
polymerase i'm walking right to do i find the three prime and i'm like oh there it is okay i'm gonna move
up oh i found the three prime five prime let me just fill this up oh i feel my nitrogenous base
the nitrogenous base that it feels is adenine so it picks into its little satchel of nucleotides it's like okay
this is adenine the complementary base for is thymine uh oh no that's not correct because you
switches from dna and rna adenine is no longer complementary to thymine in the rna it is uracil
so the dna the rna polymerase will come read find the three end read the nucleotide and say oop okay
what's the orientation we said it reads it from three to five and synthesizes it from five to three
phosphate group the three end is this oh group so it's going to kind of flip the nucleotide the opposite
uracil then when it does that it's going to go to the next one so it's going to continue it's going to go to the next
reads it finds that finds the nucleotide it says oh the nitrogenous base here is t let me reach into my satchel of a
i'm going to put my nucleotide and i'm going to flip it where it's five prime end
going down three prime end pointing up and then the nitrogenous base which is complementary to the t
is a when it does that it then fuses the three prime end and the five prime end together making a
so then it'll do what let's fix this three prime in there it'll then go go to the next nucleotide
here's the three prime end where the oh group is reads it finds the nucleotide says that
it's a g reaches into its satchel pulls out a nucleotide with the cytosine when it does it it
flips it to where the five end is on this side there's my phosphate the three prime end is upwards
and just for the heck of it because repet repetition i guess is helpful we go reads this says okay next one
here's my three prime end where the oh group is read it find the nitrogenous base it's a
sorry the guanine nitrogenous base then when it does that it situates it where the five prime end
the nitrogenous bases on guanine then it says oh my five prime n i can stitch it to the three prime end of the
now that we've done that the last thing i need you to understand is that rna polymerase is a very important
dumb and annoying but you should know it is that in eukaryotic cells we can inhibit the rna polymerase
by using a kind of toxin amanitin it's for mushrooms and this can inhibit the rna polymerase
within we'll put eukaryotic cells okay there's another drug which they love to ask in the exams as
within if it's an antibiotic that's good against bacteria prokaryotic cells so this will inhibit the rna polymerase
so this is kind of from a poisonous mushroom which is stupid to know that but they like to ask it on your exams
and then rifampicin is an antibiotic which they also love to ask okay now we've talked about elongation
we've made the dang rna rna polymerase is working real hard the last thing we got to do is we got to
the last step really that we got to discuss here is termination we've got to end this whole
and it is different in prokaryotes and eukaryotes that's why it kind of makes it a little bit frustrating
but termination is basically where we've already made our rna transcript and we just need to
detach it or disassociate it away from the dna and prevent that rna polymerase from reading
any more of the dna and making any more rna so just stop transcription how do we do that in
prokaryotes there's two mechanisms one of the ways that this happens is through what's called
road dependent termination so one is via this process called row dependent termination and it's really
simple believe it or not so let's say here we take the prokaryotics we we picked blue for our
rna polymerase so the rna polymerase here's our rna polymerase it's reading this dna as it's reading
the dna again what is it making from it you guys remember it's making the rna in this case
it could be any rna it could be the mrna trna rna whatever as it does this there's a protein called
and as it moves up the rna that's being synthesized by the rna polymerase as it gets to this rna polymerase it basically
keep breeding the dna and making any more rna no so that terminates the transcription process
all right beautiful the next mechanism within prokaryotes is rho independent termination so we
process it's a little bit more complicated and a little annoying let's say here we have the dna right and
within the dna we're going to mark these here we're going to say this is our template strand right so this strand is
the template strand right or the antisense strand and then this is going to be our coding strand
so which one does the rna polymerase read it reads the template strand or the antisense strand
there's a particular like thing called inverted repeats that form within the dna that the rna polymerase is reading
so what happens is this rna polymerase will bind to that template strand and it'll start
write these inverted repeats out in kind of a nice little color let's do let's do orange
and let's say here we have an inverted repeat where we have c c g g and then a bunch of nucleotides
that we don't care about and then here we'll have ggcc okay then we're just going to have this
is the template again on the coding strain it would just be the complementary base so if this was cc
gg right the rna polymerase is going to read this template strand what happens is right you're going to get this kind
and then it reaches this kind of like inverted repeat area and what happens is it reads this and
then basically everything you read within the template strand should be the same as it is in the coding strand
because it's the complementary base so you'll have g g c c that it'll make a bunch of nucleotides
rna is kind of coming and being transcribed from the rna polymerase something interesting happens where some
of these c's and some of these g's on this portion have a strong affinity for some of the c's and some of the g's
in this portion of the rna and as they start having this affinity they start approaching and kind of wanting to
interesting kind of like hairpin loop if you will where there's a bunch of g's and c's
within this kind of hairpin loop that are kind of interacting with one another and what happens
hop off of the dna and terminate the transcription process because what happens is once you form
thing i need you to know within row independent termination is that you'll hit this area the rna
polymerase will be transcribing reading the dna making rna it'll hit these areas of inverted repeats
when these inverted repeats are made they create this thing called a hairpin loop this hairpin loop
eukaryotic cells now how does this work this one's actually relatively simple so we had the rna polymerase in eukaryotes
as it's reading the dna it's making rna as it starts making this rna it hits a particular sequence
so it's kind of now that we know what that nucleotide sequence is let's kind of just put like this
here's that nucleotide sequence that polyadenylation signal that's been synthesized or formed by the
here this will be my polyadenylation signal this is important because we're going to talk about
is termination prokaryotes there's two ways road dependent row independent with this one you need a row protein to
the other one is row independent you don't have a row protein the rna polymerase is reading the dna
making rna and it hits these areas of inverted repeats these inverted repeats when they're made within the